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Rosertrson, '. BrRarsrorp: An Outline of a Theory of the Genesis of Protoplasmic Motion and Hxcitation.
Basepow, H.: Geological teport on Country Traversed by the South Australian Government North-West aie ac ing uxpedition, 1903." Plates x11. “to xx. tts
Lower, O. B.: New Australian Lepidoptera (xxii.)
Baker, W. H.: Notes on South Australian Decapod Crus-
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Braga, Pror. W. H. and R. D. WLEEMAN: ‘On the Alpha Particles of Radium, and their Loss of Range in eee Through Various Atoms and Molecules
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Hepiey, C.: Rerort on the Mollusca Collected by Mr. H. Basedow on the South australian Government North- west ixpedition. Plate sax.
VeERco, Dr. J. C.: Notes on South Australian Marine Mol- lusea, with Description ot New Species. Part. i: Plate XXx1.
Lower, O. b.: Description ‘ot New Australian ‘Lepidoptera, with Synonymic Notes. (Gexiias)
Basepow, H.: Un Naticoid Genera Lamellari va and Caledoni- ella, from south Australia. Plates xxvi. to xxix. :
Bragg, Pror. W. H ., and R. D. KiEEMan: On ape # Recom- bination of lons in Air and other Gases
Marpen, J. H.: An Aroid New for Australia
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Trprer, J. G. O.: Insects Collected in North-Western Region of South Australia by H. Basedow, with Descriptions of
New Species. No. Tr, ETHERIDGE, R., JUN. Additions to the Cambrian Fauna of South Australia. Plate xxv.
Baker, W. H.: Notes on South Australian Decapod Crus- tacea. Part ii. Plates: xxxil. to xxXxXvl.
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1
AN OUTLINE OF A THEORY OF THE GENESIS oF PROTOPLASMIC MOTION AND EXCITATION.
By T. Brattsrorp Rosertson, B.Sc. From the Physiological Laboratory of the University of Adelaide. ~ Communicated by E. C Stirling, M.D, F.R.S. [Read April 4, 1905.] a eo a ContTENTS.
Iutroduction ... sa qi
1, Contact Difference Ae Potential Ratton E lectro- lytes and its Influence upon Surface
Tension an tf, rs 3 . 3 2. The lon-proteid Thsotty Ub 6 3. The Chemotaxis and Galtamothen: 6 Wiiecllaler Organisms Ee ae bal 4. The Structure of Biniated Maeda eC dont D7. 5. The Contraction of Striated Muscle 7 y 29 6. On the Propagation of Excitation in Npiie ae Muscle ny 31 7. On the Normal Piece of eaten Meataid in Ger tain Tissues and their Sensibility ... pene = 8. Polar Excitation in Muscle and Nerve Bai Electrotonus aA eer Ve 9. The Influence of Verein Ouraht Deusity ee ae: 10. Tetanus and Fatigue ’ 42
11. The Work of Muscle and the Tniiienee ee Tension 44 12. The Action of Chemical Reagents upon the Con-
tracture of Muscle F. A5 13. Rhythmicity in Muscle and shé Aehion off f Inhibi- tory and Augmentor Nerves... 47 14. Rhythmicity in Nerves le at ~~ clas 15. The Movements of Plants ... van as nos 16, Summary wes om st tie ean OG INTRODUCTION.
As far as I have been able to ascertain from the litera- ture to which I have access, the theory which is put forward in this paper has not hitherto been propounded, at least in its entirety.
A number of authors have acknowledged the importance of surface tension in the vital processes of an organism,* but
* Butschli (Protoplasm and Microscopic Foams: Trans. by E. A. Minchin, 1894, page 289) gives an account of various theories as to the influence of surface tension upon the move- ments of organisms which had been put forward up to that date. In the same work he develops his own theory, which, however, is quite different in principle from mine.
2
the influence of electrolytes upon the surface tension, taken in conjunction with the ion-proteid theory, does not appear to have been worked out. Loeb* alludes to his conviction that the electrical energy of the ions in an electrolyte is trans- formed into surface energy at the surface of an organism sus- pended in it; but, as far as I have read his writings, he does not explain how this is accomplished, nor does he apply the idea. Mannf suggests that the electrical charge on colloid particles in solution may be due to the formation of definite compounds between the colloid and one or other of the ions in the solution, an hypothesis of which I make frequent use throughout this paper. Strong has developed a theory of the nervous impulse, which regards it as due to free ions in the nerve, but as he does not adopt the ion-proteid theory he is forced to make assumptions—such as the semi-permeability of proteid to certain ions—which render his theory of very limited application.
I had already written the greater part of this paper when the American Journal of Physiology for March, 1904, arrived, containing Lillie’s paper § on the toxic and anti-toxic effects of certain salts. In this he suggests that certain phenomena of movement in unicellular organisms may be due to surface tension alterations, due to ions in the medium, and he uses the analogy of the capillary electrometer ; but, as far as con- tractility is concerned he does not appear to have applied the idea or to do more than throw it out as a suggestion ; that is, so far as my acquaintance with his writings goes. Still more recently, Matthews’ paper on the nature of chemical and electrical stimulation has appeared. In this he does not pro- fess to give an explanation of the physico-chemical mechan- isms of protoplasmic movement and excitation. Nevertheless, he concludes, as I do, “that the chemical composition of the ion is of little importance compared with the importance of its electrical condition.” 41. He also considers that electrical stimulation “is due simply to the accumulation of negative
; * Jacques Loeb: American Journal of Physiology, 1902, ll., page 411
t Gustav Mamn: Physiological Histology: Methods and Theory, 1902, pages 45 and 46.
tW. M. Strong: A Physical Theory of Nerve. Journal of Physiology, 1900, vol. xxv., page 427
§ Ralph S. Lillie: The Relation of Ions to Ciliary Move- ment. American Journal of Physiology, March, 1904.
|| The Nature of Chemical and Electrical Stimulation: 1. The physiological action of an ion depends upon its elec- trical state and its electrical stability. A. P. Matthews: American Journal of Physiology, August, 1904.
§] American Journal of Physiology, vol. xi., No. 5, page 456.
3
or positive ions in different places in the tissue, or, in other words, to differences in concentration of the ions.’ *
These are the only important allusions to theories similar to mine which I have been able to find; but, as the literature to which I have access is limited, my apologies are due to any authors whose published theories I may have put forward as original.
I do not, by any means, regard the whole of the hypo- theses and deductions put forward in this paper as proved. Indeed, this paper is rather to be looked upon as providing an outline to be in the future corrected and filled in by an extended series of experimental investigations. My theory of chemotaxis, put forward in section 3, and some of my views on the propagation of excitation in muscle, put forward in section 6, are, however, upon a somewhat different footing, inasmuch as they already receive strong support from the experiments described in these sections, on infusoria, on the one hand, and on the intestine of a fly, on the other. I may state that I am about to bring forward strong experimental] evidence in support of my views in section 13 of this paper on rhythmicity in muscle, and, at the same time, of those in sections 6 and 7, on the influence of the mass of ions upon the formation of ion-proteids in excitable tissues. I also hope before long to publish further experimental evidence touching my views on the transmission of excitation, and also further experiments on chemotaxis.
In concluding these introductory remarks, I desire to express my gratitude to Professor E. C. Stirling, F.R.S., for his suggestions, for facilities afforded me for experiments, and for the interest which he has taken in the preparation of this paper, and in the experiments; to Dr. C. J. Martin, F.R.S., and to Mr. J. A. Craw, for the care with which they read the paper and for their criticisms ; to Professor W. H. Bragg, for a valuable criticism ; and to Mr. W. Fuller for his advice and practical assistance in some of the experiments. This paper was written nearly a year ago, but, owing to its having been put into the hands of others, at a distance, for their considera- tion, its publication has been delayed.
{.—Contact DIFFERENCE OF POTENTIAL BETWEEN ELECTRO- LYTES AND ITS INFLUENCE UPON SURFACE TENSION.
It is a well-known fact that when two electrolytes, or two solutions of different concentration of the same electrolyte, are in contact, there is a difference of electric potential between their bounding surfaces, just as there is a difference
* American Journal of Physiology, vol. xi., No. 5. page 457.
4
of potential at the contact surface of two metals, or of a metal and an electrolyte. Nernst explained the difference of poten- tial existing between two solutions of the same salt when the concentrations differ by the ionic theory. If a strong solution of hydrochloric acid is in contact with pure water the acid will diffuse into the water. But, since the hydrions and chloridions are capable of independent motion—the velocity of the hydrion being greater than that of the chloridion—the hydrions will travel faster into the water than the chloridions. But the hydrions carry a positive charge, while the chloridions carry a negative charge; hence the water becomes positively charged owing to an excess of hydrions and the acid solution negatively charged owing to an excess of chloridions. In such a case as this, however, as the process goes on and the water becomes positively charged, an electrostatic repulsion will be produced, tending to retard the incoming hydrions and to accelerate the chloridions. This will go on until the electrostatic repulsion is so great as to cause the hydrions and chloridions to move into the weaker solution at the same rate. As the diffusion goes on the number of ions in the weaker solution will increase, and hence the tendency of the ions to diffuse in from the stronger solution will decrease, and the electrostatic repulsion necessary to maintain the equal veloci- ties of the incoming hydrions and chloridions will diminish. Hence the contact difference of potential will, in this case, diminish as the concentrations of the two solutions approxi- mate to each other.
It is on this principle that Lippmann and von Helmholtz explained the working of the capillary electrometer, and as we shall have to consider an analogous explanation of certain vital phenomena, it may be as well to glance at the method by which the capillary electrometer re-acts to electrical forces. The capillary electrometer in its simplest form consists of a capillary tube in which mercury and sulphuric acid meet. The end of the tube dips into the sulphuric acid, which rises to a point where it is in equihbrium with the mercury, which descends the tube under a certain pressure. At the meniscus there will exist a contact difference of potential; and, since the mercury and the sulphuric acid solution are both conductors, the difference of potential will lead to an accumulation of electricity on the two sides of the bounding surface. The mercury is positive to the solution, and therefore the double layer of electricity at the bounding surface consists of posi- tive electrification on the mercury side and negative electrifica- tion on the solution side. If T be the observed surface ten- sion of the surface separating two media, and the area of this surface is increased by an amount 8, the work which is done
5
is S T. Now, the surface of separation between the mercury and acid solution with its double layer may be regarded as a condenser of which the two armatures are charged to a poten- tial difference E, where E is the contact difference of potential between the mercury and the solution.
In any condenser of which the plates are kept at a con- stant difference of potential, the electrical forces tend to increase the capacity of the condenser, and hence, in the case of this double layer, there is a tendency for the area of the double layer to increase. That is to say, that on account of the electrical forces the area of the surface of separation between the mercury and the solution tends to increase, so that the electrical forces reduce the amount of work which has to be done against the surface tension when the area of the sur- face of separation is increased. Thus, if T‘ is the value the surface tension would have, supposing no electrical double layer were present, the work done in increasing the area of the surface of separation by an amount S would be S T'. Therefore, S T, the actual amount of work done, is less than S T', the amount of work which would have been done if no electrical double layer existed, by the amount of work done by the electrical forces owing to the increase in capacity of the double layer. Thus, T, the observed surface tension, is less than T’, the surface tension 1f no double layer were present.
“Suppose the contact difference of potential between the mercury and the solution be E, the mercury being at the higher potential. Then, if an external E M F be applied so that the wire X” (leading to the mercury) “is positive, the difference of potential between the mercury and the solution will be greater than E by the amount of the applied E M F, and hence the charges on the double layer will be increased, so that the surface tension will be decreased, and to keep the meniscus in its sighted position the head of mercury must be reduced. If, however, the applied E M F is in such a direction that it acts in the opposite direction to the contact difference of potential at the meniscus, then the strength of the double layer will decrease, and hence the surface tension will increase. This increase will go on till the applied E M F is exactly equal, and opposite to the contact difference of potential, for when this occurs there will be no double layer, and hence the surface tension will possess the value w hich it would have if no electrical charges were present. If the applied E M F is further increased, then a double layer will again be formed, but with the negative charge on the mercury side. This inverted double layer. will cause a decrease in the surface tension, since the presence of such a double layer
6
must decrease the surface tension, whichever side is positive. Hence, by applying an external E M F, so as to make the mercury negative, and increasing it till the surface ten- sion, aS indicated by the pressure which has to be applied to bring the meniscus to its sighted position, is a maximum, will be exactly equal and opposite to the contact difference of potential between the mercury and the sulphuric acid solu- tion. In this way Lippmann found that the contact differ- ence of potential between mercury and sulphuric acid solution was about 1 volt.’’*
2.—TuHE Ion-PRoTEID THEORY.
This theory, due to Loeb, is that when an ionised electro- lyte diffuses into protoplasm the ions after this diffusion do not remain dissociated, but that they enter into loose combi- nation with some proteid constituent of the protoplasm, this compound being known as ion-proteid. Loeb has brought forward many facts in support of this view, t which we need not enter into here, as we shall find many even more cogent reasons for adopting it in the sequel. I will only quote, after Loeb, a statement made by Dr. W. Pauli, of Vienna: —‘We cannot doubt the general existence of ion-proteid compounds in the living organism. We have even urgent reasons for assuming that all the proteids of the protoplasm exist there only in combination with ions.” Thus it would appear that the bulk of protoplasm is formed of ion-proteid compounds, and, indeed, it seems probable that they represent the culmi- nating point of anabolism. We shall see the reasons for this view later.
If this be true, then it follows that, owing to metabolism and to dissociation analogous to the dissociation into ions of electrolytes, a number of these ions must, in general, exist in the protoplasm in a dissociated state, so that there will, in general, be a contact difference of potential between any proto- plasmic body and the (liquid) medium in which it is sus- pended. This has been directly proved by W. B. Hardy in the case of particles of albumin suspended in acid and alka- line solutions. He states his conclusions thus: —‘The proteid particles, therefore, have this interesting property: that their electrical characters are conferred upon them by the nature of the re-action, acid or alkaline, of the fluid. If the latter
* Watson: Textbook of Physics, 1900, page 814.
+ Vide On Ion-proteid Compounds and their réle in the Mechanics of Life Phenomena. American Journal of Physiology, 1900.
{ On the Coagulation of Proteid by Electricity. Journal of Physiology, June, 1899.
7
is alkaline the particles become electro-negative and wice ) versa.
It must be assumed that the ion-proteid is highly un- stable in the presence of an excess of ions, and that therefore the nature of the ion-proteid formed depends upon the pro- portions of the ions present. If this be granted (and we shall see that it is an indispensable assumption in accounting for the various phenomena observed in muscle and nerve) we can at once see that the reason for the proteid particles becoming electro-positive in an acid solution is the high velocity of the hydrion which is the characteristic ion of acids; for far more kations are diffusing into the proteid particle than anions, and therefore the ion-proteid formed is, for the greater part, kation-proteid, and the particle becomes positively charged. Similarly, in alkalies the fastest ion is the anion, and there- fore the proteid particles become electro-negative when the solution is alkaline.
3.—THE CHEMOTAXIS AND GALVANOTAXIS OF UNICELLULAR ORGANISMS.
We have now to consider the application of the prin- ciples which we have enunciated to unicellular organisms. We have seen that it is a characteristic of the proteid part of the lon-proteid molecule that it readily forms compounds with any lons which happen to be present in excess, while Hardy’s experiments, referred to in the last section, show that the electrical character of the resulting ion-proteid depends upon the relative velocities of the ions in the solution in which the proteid is suspended. In the first case, consider the effect upon a unicellular (amoeboid) organism of a constant current in the direction shown in the diagram (A =Anode, K=Ka-
FIGURE 1.
thode), the organism being supposed to be laden with kation- proteid by virtue of the metabolism and dissociation of which
8
a difference of potential is maintained between the proto- plasmic surface and that of the medium (indicated by the small + and — signs).*
Just as in the analogous case of the capillary electrometer (section 2), the effect of a current travelling from A to K will be to diminish the contact difference of potential at points such as a, which form the physiological anode, and to wmerease it at points such as k, which form the physiological kathode.
Therefore, as we have seen (section 2), the effect will be to wcrease the surface tension at points such as a, and to decrease it at points such as k. The surface, and, conse- quently, the volume cn the kathodic side of the organism will therefore wmcrease, while on the anodic side they will de- crease. The organism will, therefore, move over towards the kathode, as indicated oy the arrow—it will be “negatively gal- vanotactic.” | Consider now the effect of a similar curren upon a “negative” amceboid organism; that is, one which is laden with anion-proteid, so that the difference of potential between the protoplasmic surface and that of the medium is as represented in the diagram. In this case the contact dif- ference of potential will be increased at the physiological
A (+) (-)K
FIGuRE 2.
anode, and decreased at the physiological kathode; hence, reasoning as before, the organism will move towards the anode —it will be “‘positively galvanotactic.” The effects upon ciliated organisms will be similar, for if the diagram repre- sents one of the cilia of a ‘positive’ organism subjected to a constant current in the sense indicated, the P.D. (difference of
* As such organisms are electro-positive to the solution in which they are suspended, I will in the future distinguish them as ‘‘positive,’’ those which are laden with anion-proteid being designated ‘‘negative.’’
FIGuRE 3.
potential) at the surface forming the physiological anode will be diminished, and that at the physiological kathode increas- ed; hence the former surface will diminish owing to the in- creased surface tension, and the latter will increase ; hence the cilium will bend towards the anode, as indicated by the small arrow, and the organism will be propelled towards the kathode —it will be “negatively galvanotactic.” The effect of the same current on a ‘“‘negative” ciliated organism will, of course, be the reverse. Hence, we may formulate the rule that “positive” organisms will be attracted to the kathode, and “negative” organisms to the anode. When a very strong current is passed, the lowering of the surface tension at kathodic points in a “positive” organism or at anodic points in a “negative” organism may be so excessive that the parts of the surface no longer colijre, and the organism breaks up. This is the ex- planation of the uisintegration of certain organisms under the action of a constant current, e.g., Pelomyxa.* The effect of the constant current upon organisms which are neither “nega- tive’ nor “positive”—that is, which are equally loaded with anions and kations—must obviously be attraction to hoth elee- trodes, since a contact P.D. would be artificially produced at both surfaces: thus, such organisms would not exhibit any marked preference for either electrode. We have now to consider the effects of chemical re-agents upon these organisms.
From the point of view of the theory which I have put forward, the phenomena of chemotaxis must be attributed to the diffusion of the ions in the re-agents into the protoplasm in different proportions. Consider the effect upon a “‘posi- tive” ameceboid cell (A, Fig. 4), of a salt such as KCl, in which the kation has a greater velocity than the anion, diffus- ing from a capillary (B). Since the quicker-moving kations will diffuse faster than the anions, more kations will enter the
* Verworn: General Physiology: Trans. by Frederic S. Lee, page 419.
10
organism, in a given time, than anions; that is, the contact P.D. at points such as a (Fig. 4), will be augmented, and
FIGURE 4,
at points such as / unaffected or much less augmented (since the concentration of the KCl is as the inverse square). Hence the surface tension at } will be greater than that at a, and the organism will move towards the capillary.
With a salt like CaCl,, in which many more anions would enter the organism, in a given time, than kations, the reverse would be the case.
If the organism were ‘negative’ the above effects would be reversed.
Of course, leaving a “positive” organism within the sphere of influence of CaCl, for a sufticient time would convert its initial repulsion from the CaCl, into attraction, for the organism would become “‘negative” owing to the excess of anions entering from the CaCl,. Similarly, a “ negative ” organism, exposed for too long a time to the influence of a re-agent in which the kations move faster than the anions (e.g., KCl, or an acid) would become “positive.”
“Isotactic”” organisms—as we may call those organisms which are equally loaded with anions and kations—would, of course, be attracted by both kinds of re-agents, for an arti- ficial P.D. would be established on the side nearest the re- agent, and the surface tension therefore decreased at those points: but, as this P.D. would be very small except in organisms quite close to the capillary, such organisms would exhibit no marked re-action.
11
The theoretical results at which we have arrived may be tabulated as below : —
Nature of Re-agent.
a State of | —— | — Calv Organism. _ Kation faster | Anion faster | ralvanotaxis.
| than Anion. | than Kation.
a <A it aR iene nies Positive | Attraction | Repulsion Attraction to Kathode Negative | Repulsion | Attraction | Attraction to Anode Isotactic | Attraction | Attraction pleoerne to Anode
and Kath ode
The stimulation effect of a re-agent will be proportional to the difference of potential between the organism and the
U Vv
medium. This will be a itiaal niin ies Where & is a constant (Oh ey i) ec,
(the temperature being constant), ~ and v are the velocities
of the kation and anion respectively, y, and y, are
their valencys respectively, and c, and c, are the con-
centrations of the electrolyte in the medium and in the
: ° : C . . organism respectively.* If —2 be constant, and it is_pro- : c 1 bably nearly so when equivalent solutions are used throughout, we have that the stimulation effect of an electrolyte is propor-
U w tional to Y¥, Y.2, which we may call the ‘stimulation
Uu+uwv
e
is Hittorf’s
efficiency” of the electrolyte.+ Since , ’ ute
“transport number,” and is usually denoted by 7, the stimu-
: au —-n Mn lation etticiency may also be expressed by ——, which
Y1 Ye
reduces to 1 —2n, if the ions are mono-valent.
We cannot assume, it is true, that the stimulation effects of different re-agents will be strictly proportional to their
*Vide Whetham: A Treatise on the Theory of Solution, 1902, page 382.
+ I originally defined the ‘‘stimulation efficiency” as — which, of course, is only true for univalent ions. I am indebted to Mr. J. A. Craw for the above correction.
12
“stimulation efficiencies’ partly because it is uncertain whe- C : .
ther —2, referred to above, is constant, and also because of c
the ion-proteid already present in the organism, the influence of which will be to lessen or to increase the effect of the testing re-agent. Still, the “stimulation efficiency” of a re- agent will serve as a rough index of its probable effect, and I therefore append a rough table of the re-agents most com- monly used as stimuli in physiology, with their ionic veloci- ties and “stimulation efficiencies,” the sign + before the stimulation efficiency denoting attraction of a “‘positive” organism, and the sign — _ attraction of a “negative” organism.
If the stimulation efficiency be calculated from the ionic velocities 1t will not be accurate except for very dilute, com- pletely ionised, solutions. A more accurate method is to cal- culate the stimulation efficiency from the value of the trans- port number 7, at the dilution which we are using. But, in order to make the table more general, I have, except in the cases of the carbonates and MgCl,, calculated the stimula- tion efficiency from the ionic velocities. It 1s necessary to bear in mind, however, that solutions of a salt formed by the neutralisation of a strong base by a weak acid, as, for example, Na,CO,, always contain OH ions, which have a very high velocity, and which tend to render the stimulation efficiency negative. Finally, in order to observe any propor- tion between the stimulation effects of different re-agents we must use equivalent solutions. The ionic velocities of Cu, Ba, Ca, SO,, and Ag, in the accompanying table, are taken from the results given by W. C. D. Whetham in the Philosophical Transactions of the Royal Society.* Those of Cl and I are from Kohlrausch’s results, quoted by Whe- tham.+ | Whetham found that his results, obtained by a direct method, corresponded very closely with Kohlrausch’s. Those of K; Na, Li} H, NO,;, “and OH are ‘from Kener rausch’s results quoted by Watson.[ The stimulation effi- ciencies of K,CO,, Na,CO,, and MgCl, are calculated from the transport numbers for dilute solutions (029, ‘093, and 087 equivalent gramme molecules per litre respectively) given in Fitzpatrick’s ‘““The Electro-Chemical Properties of Aqueous Solutions.’’§
* Vol. clxxxiv. A, page 387; and vol. clxxxvi. A, page 507. + Thid. +t Textbook of Physics, 1900, page 798.
§ British Association Report, 1893. Reprinted by Whetham in his Theory of Solution and Electrolysis.
13
The re-agents are in the order of their ‘‘stimulation effi- ciencies.”’
TABLE OF STIMULATION EFFICIENCIES. | Velocity of Kation Velocity of Anion Sti : eee F wi sal Claniinebe } imulation "5 adhe wy apg es ee appa plete eer ga ISIE | | ———__—_—_—_|— Polos) aes ae £8) Ne ae
H.SO, thd B90 x1 OOS THU O=" Soe 1, HCl DP RIOD IOS ONG SP O=o 1) BUTTE HNO, “axe S20 Ore? | Gate 10> 4 “667 KECO; ot —- —— + 547 K.SO, nee O6*x-10>" 7 Oe cy oe bs Na,CO, oe — — + 289 Na,SO, ae ae 1Oro | Aye xen Oe + -250 KCl hed: 66° x On re Or + -109 KI _ Cox 10 COE tO= + ‘048 KNO, shes 6635010 Oe LO +° O15 NaCl at 2215 jee cal h) ka Nox = -082 CuSO, a BM ele lee to tO — -092 AgNO, sie fot ae Osx hu = -133 Nal uel Py eer OC cos — *}45 NaNO, a AD ee” (yd veel! mae — 174 LiCl nb 30 Le ee Oss =e BaCl, te BS eal 4 iS iroceng A a — -364 CaCl, See a inp Gen Ce Be ox LOT i 4) CuCl, ne le Ore aye ye ed N — -446 KOH bed 66 x 10~° HG oxa ae — -468 MeCl, ae —- — -— D17 NaOH EY Za a UL ape L822 Os, = O04 LiOH ero 36. xlOee Lee cele — 670 Ba(OH), ae 39: x, LO. ise a es Ses. Ca(OH), fis ose One (e2ux Te" eh ele
The third decimal place in the column of stimulation effi- ciencies is the nearest approximation.
To test the conclusions arrived at in this section, it is necessary to ascertain the state, ‘‘positive” or “negative,” of the organism, and then to test its re-actions to various re- agents, and to the constant current, under the same condi- tions.
This appears not to have been done hitherto. H. H. Dale, it is true, has made investigations of this nature,* but he nearly always uses acetic acid in his media or in his test
* Journal of iPhecolocy, 1901, ae a Tee 991.
14
solutions. For our purposes this choice is most unfortunate, as the dissociation of acetic acid is very small, even in dilute solutions ; indeed, it is only half dissociated when the solution contains only about two parts of acetic acid per million.* Moreover, the amount of hydrion due to acetic acid is greatiyv reduced on its diffusion into a medium containing highly ionised salts (as was the case in Dale’s experiments), while the acetanions are not correspondingly reduced, and the resultant proportions of ions depend upon the electrolytes into which it is diffusing.+ Hence the theoretical effects of acetic acid are highly uncertain, and this corresponds with the uncertainty
of Dale’s results. Such sources of ambiguity do not arise when we use strong acids in dilute solution and_ perfectly ionised solutions of salts. A number of other investigators
have tested the effects of various re-agents upon unicetliilar organisms, but as they did not previously ascertain the nature of the ions in the medium in which the organisms were tested their results tell us nothing with regard to this theory. I there- fore carried out a series of experiments with a view towards systematically testing the accuracy of the conclusions put forward in this section. The organisms used were the infu- soria in the large intestine and rectum of a frog (Ranaodea aurea). Four species were found and used in these experi- ments, namely:—1. A species of Spirostomum, closely resem- bling, if not identical with, S. ambiguum. 2. A species of Opalina, probably Opalina ranarum. 3. A large disc-shaped species, more than half the length of Spirostomum sp., and nearly as wide as it is long, much flattened laterally, endo- plasm in front of the mouth, triangular in shape, slightly re- curved. 4. A much smaller species, only about half the length of Opalina sp., but otherwise resembling the last-men- tioned species. The two latter species, in the absence of any expert knowledge of the subject, [am unable to name. I will, therefore, designate them, respectively, species A and species B.
A cell of wax was made on a glass slide. It measured about # in. square, and the walls were about 1 millimetre deep. In two opposite walls of the cell were grooves, which were the same depth as the walls. A small portion of the intestinal or rectal contents was placed in the cell, and a large drop of a given solution, the medium, was placed in the cell with it. This was left for a varying period, and then a cover-glass was placed on the cell, any spaces in the cell being
* Walker: Introduction to Physical Chemistry, third edition, page 236.
_ + Vide Walker: Introduction to Physical Chemistry, third edition, pages 304 and 816.
15
filled up with some more of the solution. Capillaries con- taining the test-solutions were then inserted through the grooves, so as to project slightly into the cell, and the re- mainder of the capillary was sometimes slightly raised by resting it on slips of paper, in order to aid diffusion. by gravity. The various parts of the cell, etc., are indicated in the diagram (Fig. 5). The cell was then examined under the low power of a microscope, or with a magnifying glass.
FIGuRE 5.
The object of placing the organisms first in a known medium was to ensure their being “positive” or “negative,” as desired. Thus an organism which had been placed for ten minutes in a decinormal solution of KCl would be positive, owing to the excess of kations which had entered it ; and its reaction, if our reasoning has been correct, should be attraction to a solution with a positive stimulation efficiency, and repulsion from a solution with a negative stimulation efficiency. Of course, it is quite uncertain what salts have been introduced with the rectal contents, but as the proportion of rectal con- tents in the cell to the volume of the medium was, in each experiment, small, the influence of the introduced salts was negligible. The results of the experiments, as the accom- panying table shows, are in entire harmony with the theory I have put forward—in every case the theoretical and actual results are the same. Experiment No. 14 might be thought to be an exception, but when we remember the extremely low stimulation efficiency of KNO,, and that its effect might be very easily neutralised by small quantities of salts with nega- tive stimulation efficiencies introduced with the rectal con- tents we see that the organisms, in this case, were very pro- bably isotactic. It will also be observed that the re-action always takes place quickly when media with a high stimulation efficiency were employed ; and delay, as in experiment No. 9, only occurred when the stimulation efficiency of the medium was low. As there were generally individuals of more than one species in the cell, some of the results were obtained sim- ultaneously, e.g., experiment No. 3 gave results for Spirosto- mum, Opalina, and species B.
16
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26
It was found that Spirostomum sp. was an ideal species for these investigations, as it was not injuriously affected by the solutions, and was very active and sensitive to the test solu- tions. Species A and B were also uninjured by the solutions, but did not, as a rule, re-act quite so quickly as Spirostomum sp. Opalina was very liable to injury by decinormal solutions —the action of KCl and of NaCl in this respect was capri- clous—sometimes decinormal solutions appeared to kill the organisms, sometimes not. Decinormal solutions of Na,CO,, CaCl,, and BaCl,, were very injurious to Opalina, the two latter causing almost immediate disintegration, doubtless owing to their high stimulation efficiency causing excessive lowering of the surface tension. Decinormal KOH killed all the species and caused disintegration, doubtless, again, on account of its bigh stimulation efficiency.
The galvanotaxis of these organisms was also tested. The ordinary stimulation trough, with parallel sides of porous clay, described by Verworn,* was employed, and non-polaris- able brush electrodes were used to lead in the current. The following results were obtained . —
1. Rectum of a frog left in tap water overnight. Some of contents placed in KCl in the stimulation trough and
left for a quarter of an hour. Then tested with three two-volt storage cells. Opalina all dead. Species B numerous, their rotatory movements became slower and tended towards the kathode. In ten minutes the anodic half of the trough was deserted, and the kathodic half well populated, especially near the kathode.
N > e eS 2. Some of contents of same rectum placed in a0 CaCl,
for a quarter of an hour. Opalina all dead. Species B numerous. Tested with three two-volt storage cells. Organ- isms proceeded with an irregular, wavy motion towards the anode, and in a few minutes had formed a small cluster there, which remained unaltered. Several individuals, however, 1e- mained in the kathodic, half of the cell.
3. Rectum left forty-eight hours in tap water. Some of contents placed in Tia a,CO,, and left for half an hour. Tested with ten two-volt storage cells. Organisms scanty, con- sisting of Opal/ina and species B. Both to kathode, the athrac- tion of species B being hampered by its rotatory movemeuis. In half an hour a small cluster had formed at the kathode.
* Verworn: Genera! Physiology: Trans. by Frederic 8.1 page 416.
bo ~l
N
4. Some of contents of same rectum placed in 70% I, and left for half an hour. Tested with ten two-volt storage cells. Opalina and species B, both to kathode. After half an hour still at kathode, where they had formed a small cluster.
Thus the results of these experiments on galvanotaxis in different media also go to support the theory I have put for- ward. In addition, it may be mentioned that the results of Dale’s experiments in galvanotaxis go generally to support this theory.* Thus, Balantidiwm duodeni shaken into solu- tions of increasing acidity collected closely at the kathode when the solution contained ‘02 per cent. HCl, the current being six pint bichromate cells. The same species in pure ‘6 per cent. NaCl went to anode with moderate currents, and to kathode with twelve cells. The latter result I believe to be due to the acid liberated at the anode causing the organisms to become “positive.” Dale also found that Opalina in ‘6 per cent. saline and ‘01 per cent. NaOH collected at the anode, and that Vyctotherus did the same when left in the solution for a sufficient time (ten minutes), and other instances, in which he used only specified inorganic solutions, will be noticed on referring to Dale’s paper.
4. THe STRUCTURE OF STRIATED MUSCLE.
The following is extracted from Schafer’s “Essentials of Histology,” sixth edition, page 102 : —*‘The sarcostyles are sub- divided at regular intervals by thin transverse disks (mem- branes of Krause) into successive portions, which may be term- ed sarcomeres; each sarcomere 1s occupied by a portion of the dark stria of the whole fibre (sarcous element). The sarcous element is reaily double, and in the stretched fibre separates into two at the line of Hensen. At either end of the sarcous element 1s a clear substance (probably fiuid or semi-fluid), separating it from the membrane of Krause. This clear sub- stance is more evident the more the fibril is extended, but diminishes to complete cisappearance in the contracted muscle. The cause of the change is explained when we study more minutely the structurc of the sarcous element. For each sar- cous element is pervaded with longitudinal canals or pores, which are open in the direction of Krause’s membrane, but closed at the middle of the sarcous element. In the con- tracted muscle the clear part of the muscle substance has disappeared from view, but the sarcous element is swollen and the sarcomere is thus shortened ; in the uncontracted muscle,
— —
*“ H. H. Dale: Galvanotaxis and Chemotaxis of Ciliate Infusoria. Journal of Physiology, 1901, page 291.
28
on the other hand, the clear part occupies a considerable in- terval ketween the sarcous element and the membrane of Krause, the sarcomere being lengthened and narrowed. The sarcous element does not lie free in the middle of the sarco- mere, but is attached at either end to Krause’s membrane by very fine lines, which may represent fine septa, running through the clear substance: on the other hand, Krause’s membrane appears to be attached laterally to a fine mem- brane, which limits the fibril externally.” Page 105:— “Comparing the structure of the sarcomere with that of the protoplasm of au ameceboid cell, we find in both a framework (spongioplasm, substance of sarcous element), which tends to stain with haematoxylin and similar re-agents, which encloses in its meshes or pores a clear, probably semi-fluid, sub- stance (hyaloplasm, clear substance of sarcomere), which re- mains unstained by these re-agents. In both instances, also, the clear substance or hyaloplasm, when the tissue is sub- jected to stimulation, passes into the pores of the porous sub- tance, or spongioplasm (contraction), whilst in the absence of such stimulation it tends to pass out from the spongioplasm (formation of pseudopodia, resting condition of muscle). Thus, both the movements of cell-protoplasm and those of muscle seem brought about by similar means, although at first sight the structure of muscle is so dissimilar from that of protoplasm. We have already noticed that the movements of cilia are susceptible of a similar explanation.”
Krause’s Membrane
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yt t
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29
It would thus appear that the structure of the sarcomere may be regarded as that represented in the diagram. If the walls of the sarcous element be elastic, it is obvious that the surface tension (T) of the fluid hyaloplasm would pull them in at all points along their surface of contact, while on dimi- nution of the surface tension the sarcous element would swell in order to increase the surface of contact, and, since nothing but hyaloplasm is available to fill up the space thus created, hyaloplasm will flow ato the sarcous element. If the surface tension is increased the operations would be reversed.
I am aware tkat histologists are not unanimous in adopt- ing this theory of the structure of striated muscle, but. it enables us to obtain a clear view of the influence of the sur- face tension of the hyaloplasm upon the contraction of muscle.
5.—THE CONTRACTION OF STRIATED MUSCLE.
In order to explain the contraction of striated muscle we must assume that there is a contact difference of potential be- tween the spongioplasm and hyaloplasm, due to the presence of kation-proteul in the muscle. That kation-proteid is pre- sent in striated muscle is demonstrated by the second part of Hermann’s law, namely, that muscle becomes negative when dying, that is, that within the muscle there is an E.M.F. tending to produce a current from the dying points to the other points in the muscle.* If “when dying” be taken to mean “when injury of such a nature as to set up katabolism is applied” we may at once state that this is due to the libera- tion of kations by the decomposing ion-proteid.
Similarly, muscle becomes ‘‘negative’’ when excited to activity, because the excitation sets up katabolism, and kations are set free. We shall go more fully into the influence of the electric current upon the katicn-proteid in the sequel ; but, in passing, we may note Biedermann’s statement that if the pas- sage of a weak “polarising” current through muscle be con- tinued, its excitability is first augmented and then dim- inished.t | We can easily see that while the katabolic pro- cesses are being hurried up by the polarising current, any additional excitation will precipitate them the more easily because the ion-proteid 1s already partly decomposed, while, as the constant excitation and consequent katabolism continue the supply ‘of kations becomes so diminished that it can no longer respond to the demands of additional excitation. That
* For an explanation of this confusion in physiological ter- minology, vide Waller: Human Physiology, 1896, page 388.
+ Biedermann: Electro-physiology: Trans. by F. A. Weiby, vol. i., page
30
such continuous excitation does take place during the passage of the polarising current is a conclusion definitely arrived at by Biedermann. He says:—“The electrical current sets up a process of excitation in striated, as in smooth, muscle throughout the duration of its passage.’* Assuming, for the moment, what is about to be proved, namely, that the setting free of kations by the current is the cause of contraction, we see that the fact that maximal twitches are much higher with a constant than with an induced current; is due to the greater amount of decomposition of kation-proteid by the cur- rent which acts the longer time.
As to the nature of the kations which form the 1on-proteid in the hyaloplasm of striated muscle, we can say very little. The effects of chemical re-agents on muscle show, as we shall see later, that simple metallic ions are capable of forming ion-proteids in muscle just as in unicellular organ- isms. Probably K and H ions play an important part—as it is well known that KH,PO, is always formed when muscle becomes rigored—and, moreover, K salts predominate in the ash of muscle, Ca and Mg only being present in traces. {
Now, it is evident that, since hyaloplasm is laden with kation-proteid, the recult of its katabolism or dissociation must be the formation of an electrical double layer at the cohtact surface of the byaloplasm and spongioplasm by the deposition of ions, just as in the case of the contact surface between the mercury and sulphuric acid solution in the capi!. lary electrometer.
The action of a stimulus, such as an electric current, os muscle, is to set up katabolism at certain points in the muscle (¢.g., the kathode on make), and the consequence of this is, as we have seen, to cause “‘negativity”’ at such points in consequence of the kations set free. This “negativity” is transmitted, practically unaltered, § along the muscle, and its mode of transmission will be discussed in detail in the sequel.
It remains to consider the effect of the progress of this area of high potential along the muscle. It will be, as ex- pressed by Bernstein’s “wave of excitation,” || to uninterrup-
* Biedermann: LElectro-physiology : Trans. by F. A. Welby, vol. i., page 185.
t Lbid«; volais paze 176;
{ Starling: Elements of Human Physiology, fifth edition, page 130.
§ Biedermann: Electro-physiology: Trans. by F. A. We'by, vol. i1., page 395.
|| Ibid., vol. 1., page 374.
31
tedly raise the potential at each point in the muscle and un- interruptedly let it fall again. The effect of this will be (just as in the capillary electrometer when the potential on one side of the meniscus is raised) to diminish the surface tension at the contact surface of the spongioplasm and _ hyaloplasm owing to the increase in the P.D. between them.
Now, if we suppose the walls of the sarcous element to be elastic—the effect of the surface tension of the hyaloplasm will be to exert a pull inwards upon the wall—and therefore taeys walls: -are . pulled. in. To this. pull. .the wall will cffer a resistance owing to its elasticity. If these two forces are in equ'librium, increasing the surface tension will narrow the tube, while diminishing the surface tension will widen it. But widening this elastic tube must shorten it, just as an indiarubber tube when stretched longi- tudinally grows narrower, and when stretched laterally grows shorter. The sarcous element, in shortening, must exert a pull on the fine fibrils which, it is conjectured, attach them to Krause’s membrane; heice, the two membranes of Krause are pulled together and the muscle contracts. Hence, since the “wave of negativity” must diminish the surface tension— mot by deposition of ions, for in that case 1t would undergo excessive decrement, which it does not*—but by simply rais- ing the P.D. between the hyaloplasm and spongioplasm it must give rise to a contraction.
6.—ON THE PROPAGATION OF EXCITATION IN NERVE AND MUSCLE.
We have seen that the hyaloplasm of striated muscle con- tains a kation-proteid owing to the presence and metabolism of which the surface of contact between the spongioplasmic sarcous elements and the hyaloplasm is always positively charged on the nyaloplasmic side, or, in physiological termi- nology, the surface of the hyaloplasm is always “‘negative” to that of the spongioplasm. When any breaking up of the kation-proteid takes place, kations must therefore be set free. Now, I have previously pointed out that the fundamental property of ion-proteid is that it is very unstable in the pres- ence of ions, tending to form new ion-proteid compounds with any ions which may be present in excess; and, indeed, it is upon this property of the ion-proteid that the phenomena of contraction and irritability in living tissues depend. I may now throw this assertion into a more definite form, and state that when a certain minimal number of free ions (the number varying in different tissues) is present at any point in an excit-
* Biedermann: Electro-physiology: Trans. by F. he Weiby, vol. i., page 395.
32
able tissue, the mass influence of these ions will be sufficient to displace the ions already holding the proteid molecule, and to take their place. Hence the kations set free in one section of an excitable tissue by excitation may in turn dis- place others in the next section of ion-proteid material, which again may set free ions in the following section, and so on, so that a wave of excitation is propagated through the tissue. Thus we conclude that the “‘wave of negativity” does not pro- gress so much by diffusion as by a process of successive dis- placement.
The evidence for this fact will come out more clearly in the sequel, but we may allude to some of the facts supporting it now. Just as in muscle, we consider that there is present in the axis cylinder of nerve a kation-proteid which, by its katabolism under stimulation, gives rise to a wave of nega- tivity, only, as in this case there is no elastic surface for ions to be deposited on, no contraction is evoked. Now, the exci- tatory state evoked in nerve by an intense stimulus is propa- gated more rapidly than that caused by a weaker one.* We can easily see that this must be due tv the greater mass of kations set free initially ; they would more easily and quickly set free other ions in each section (for it is the principle of mass action that the rate of chemical change depends upon the masses of the re-acting substances). This will be seen more easily when we come to consider the genesis of the discharge in the heart; but it is obvious that if the wave of negativity were propagated by mere diffusion, since the number of ions set free in no wise affects their velocity, the intensity of the stimulus could not affect the velocity of the excitatory wave.
Of a similar nature may possibly be the explanation of the fact that nerve cells conduct more slowly than nerve fibres.t The cross-section of a nerve cell is much greater than that of its fibre; hence at any moment the same number of ions would have very many more ion-proteid molecules to cope with than they had during their course in the fibre.
Another line of evidence supporting the theory we have put forward is the influence of various solutions of salts upon the transmission of excitation. If a portion of a conducting excitable tissue were immersed in a solution with a negative stimulation efficiency, and a wave of negativity initiated else- where, on passing through the immersed portion (if it travels by displacement) should either be diminished, abolished, or converted into a wave of positivity, according as little or
* Gotch: Schafer’s Textbook of Physiology, vol. li., page 458. + Biedermann: Electro-physiology: Trans. by F. A. Welby, vol. i1., page 69.
33
much of the muscle-proteid was taken up by the anions of the solution. Of course, the wave of positivity thus produced, on issuing from the region immersed, would be converted into a wave of negativity again, owing to the anions displacing kations ; but it would probably be reduced owing to some of the anions combining directly with kations. ‘Lhis idea re- ceives support from the fact that nerves which have been im- mersed for a long time in salt solution, and are repeatedly stimulated, give a wave of positivity.* Still more suggestive is the fact that the excitatory state is often diminished when passing through a portion of nerve treated with NaCl—abso- lutely with a 61 per cent. Nal solution—though excita- bility is still present.; Thus the wave of negativity is, in the second instance, suppressed, as we have said it may be, though a wave may be started from the point affected by direct action of the current. The reason why the wave is so absolutely suppressed in the case of Nal is probably the high stimulation efficiency of Nal causing a great predominance of anions; as we shall see, the number of kations in a normal wave of negativity in medullated nerve is small.
It will be obvious that there is a difficulty in proving this point in nerve, because the wave of positivity in the affected region is converted into a wave of negativity directly it emerges. But our previous investigations into the contrac- tion of muscle show that a wave of positivity cannot cause a contraction until it be converted into a wave of negativity, because a wave of positivity would only diminish, not increase, the P.D. between the hyaloplasm and spongioplasm, and, therefore, the surface tension at their contact surface would not be diminished, and no contraction would ensue; hence, a portion of a muscle which has been treated with a solution which has a sufficiently great negative stimulation efficiency ought to act as a motor nerve to the rest.
This can be very easily demonstrated in the intestine of a fly. In insects the walls of the intestine contain “striated (uninuclear) muscle cells, which by contraction set up the nor- mal peristaltic movements of the digestive tract.’’+ The species I used for experiments was Callophora villosa, Desv., which is the Australian representative of the English blue- bottle. If the last posterior segment of one of these flies is torn away with forceps, the end of the intestine is usually left hanging from it, and, if the operation be performed care- fully, nearly half an inch of intestine can sometimes be
* Gotch: Schifer’s Textbook of Physiology, vol. ii., page 538. + Gotch: Schifer’s Textbook of Physiology, vol. ii., page 490. t Biedermann: Electro-vhysiology : Trans. by F. A. Welby. vol. i1., page 164. '
34
obtained. If this be placed on a slide which has been slightly wetted with a decinormal solution of NaCl, and the super- fluous fluid taken up by filter paper, on examining the in- testine under the miscroscope peristaltic waves of con- traction are seen travelling down the intestine towards the rectum at an easily followed, uniform velocity, with moderate frequency. On now touching the intestine at about its middle point with a fine pointed camel’s hair brush, which has been just wetted with a decinormal solution of CaCl,, a remark- able effect is observed : —If one of the peristaltic waves start- ing at the end of the intestine furthest from the rectum be followed with the eye, it is observed to completely disappear on entering the region which has been treated with CaCl, ; but if we continue to move the eye along the intestine at the same rate as the wave of contraction was formerly moving, on reaching the other end of the affected area the wave will be seen to emerge from it as vigorous as before, and to be travel- ling at the same rate. Thus, contraction has been abolished by the CaCl,, while conduction continues to take place at the same rate as before. The suppression of the wave of con- traction in the area affected is not due to any apparent change in form in the intestine in that area, for if the CaCl, be properly applied, no apparent change in form takes place. If, however, too much CaCl, is applied—so that it is not sufficiently diluted by the NaCl present (e.g., a small drop)— the intestine at that part is thrown into corrugations which represent fixed contractions ; that is, the intestine at that part acquires “tone” (the cause of this will be considered later), but this does not alter the effect of the CaCl, upon incoming waves of contraction, which enter, and are suppressed, and re-appear at the other end of the affected region as before. Care must be taken in these experiments not to have the in- testine too wet, otherwise it is difficult to confine the effect of the CaCl, to a given region, as the CaCl, is carried about by currents in the water. I repeated this experiment a number of times, and, when the above-mentioned precautions had been taken. I never failed to get the effect described. I also obtained the same effect using a decinormal solution of BaCl, instead of CaCl,. On glancing at the table of stimulation efficiencies in section 4, it will be seen that both CaCl, and BaCl, have high negative stimulation efficiencies, so that our theoretical deduction is confirmed by these experi- ments. The action of CaCl, and BaCl,, when applied to a limited region of the intestine, may be contrasted with that of a decinormal solution of KCl when similarly applied, al- though no more apparent change of form is produced in the intestine by the KCl than by CaCl,; yet not only is the
35
wave of ccntraction suppressed in the region treated v:tn KCl, but also the wave of excitation, inasmuch as no wave of contraction issues below the part affected—all parts of the intestine below that treated with KCl remain motionless, while those above that part are in vigorous peristalsis. This action of KCl in abolishing both contractility and _ excita- bility in the intestine of the fly is only an instance of its general effect upon contractile tissues, the cause of which will be discussed later.
7.—On THE NORMAL PRESENCE OF ANION-PROTEID IN CERTAIN TISSUES, AND THEIR SENSIBILITY.
A fact which it is important to realise is the normal presence of a certain amount of anion-proteid in irritable tissues. it is easy to see that this is a priori probable, for, since the blood and lymph contain ions of both kinds, it is to be expected that some anions would be taken up and formed into anion-proteid. But confirmatory evidence is not far to seek: the cardiac inhibitory vagus fibres, when excited, pro- duce a positive variation of the muscle current; this can only be due to anions released by the nervous impulse, and since “as regards their galvanic re-action to excitation they differ in no respect from other nerve fibres,’* these anions must be displaced from anion-proteid in the muscle itself, or in the nerve endings. The “staircase”? phenomenon, that is, the improvement of each of the first few contractions of a muscle by the one that precedes it, which is specially notice- able in the heart, and in the swimming bell of medusz,7 is direct evidence of the fact that the wave of negativity is not propagated by mere diffusion ; for some chemical change evi- dently takes place wherever the wave passes, since the i1m- provement is not confined to the point stimulated, but occuys at all points traversed by the wave of negativity.[ I attri- bute the “staircase” to the presence of a small amount of un- stable anion-proteid, which tends to accumulate, and is mostly removed by the first few waves of negativity, the kations of which displace the anions. We should note that the “stair- case” is not always comparable with the cumulative effect of sub-minimal stimuli on many tissues, so that they eventually become capable of causing discharge 1nd evoking contraction. In this case, no doubt, the kations accumulate, being added
* Biedermann: Electro-physiology, vol. ii., page 257.
+ Vide Romanes: Jellyfish, Starfish, and Sea-urchins, Int. sc. ser., page 56.
+ Romanes: Jellyfish, Starfish, and Sea-urchins. Int. se. ser., page 57.
36
to by each stimulus until at last they reach the necessary minimum required to displace ions from the ion-proteid. The same principle explains idio-muscular swellings—fixed waves of contraction of small extent; these are due to the kations set free not being sufficient to cause a discharge by displacement, but sufficient to augment the P.D. between hyaloplasm and spongioplasm, and so cause local contraction —while the same principle, together with the presence of anions, explains the local extension at the anode seen in some muscles ;* anions are liberated, as in ordinary electrolysis, at the anode—the P.D. between the hyaloplasm and_ spongio- plasm is diminished, and the muscle extends; but, as kations are predominant, the anions are not strong enough to cause displacement, and so the excitation does not travel. Some- times the P.D. is so far reduced that the muscle extends so much as to break at the anode;+ such a result could not, cf course, take place unless the muscle had, normally, a good deal of ‘‘tone’—that is, there is considerable room for exten- sion and free kations are numerous.
This leads us directly to the consideration of the “threshold number” of a tissue—that is, the number of ions necessary to cause a discharge in a given tissue (the inverse of which is proportional to the “sensibility” of the tissue). If we call this number per unit cross-section 6, it is evident that @ must vary considerably in different tissues, and that the greater P is the slower will be conduction of excitation, for at each successive point more time must be allowed for the ions to gather. Since in non-medullated nerves the rate of conduction is much lower than in medullated nerves (8 metres per sec. in the former, 27 per sec. in the latter{) we may state provisionally that § is greater in non-medullated nerves than in medullated. This is confirmed by the fact that non-medullated nerve re-acts better to stimuli of prolonged duration than to short induction shocks, § for more time is required by the electric current to liberate P ions in non- medullated nerves than in medullated, in which extremely short current duration is sufficient.|| The conductivity of medullated nerve, and, indeed, of all excitable tissues, is lower-
* Biedermann: Electro-physiolvzy : Trans. by F. A. Welby, vol. i1., page 236.
+ Ibid., vol. 11., page 239.
+Goteh: Schifer’s Textbook of Physiology, vol. ii., pages 455 and 482.
§ Ibid., vol. il., page 284.
| Ibid., vol. ii., page 475; and Biedermann: Electro-physi- ology: Trans. by F. A. Welby, vol. ii., pages 121 and 122.
a
es
37
ed by lowering the temperature.* This means that / is raised, therefore the excitability to short-duration stimuli is lowered.+ Since conduction is much slower in smooth than in striated muscle, # must be greater in the former, and the minimal duration of excitation, in order to cause contraction, is therefore greater in smooth than in striated muscle. And, indeed, Biedermann states generally that the excitation of more sluggish excitable tissues depends on the duration of the stimulus.{ The conductivity of muscle is lowered by lower- ing the temperature, but the height of the contractions is augmented :§ this is because of the greater value of 6 caus- ing a greater P.D. on excitation. Since the rate of propa- gation in the heart is less than in striated skeletal muscle (1°5 metres per sec., as against 3 metres per sec.)|| (@ is pro- bably greater in heart muscle than in ordinary striated muscle.
8.—PoLaR EXcITATION IN MUSCLE AND NERVE AND ELECTROTANUS.
One of the most striking facts in the electrical stimula- tion of muscle is that the make contraction starts at the kathode, and the break contraction at the anode. From my theory, however, it seems to obtain a sufficiently simple ex- planation. On the passage of the electric current the ion- proteid undergoes decomposition, and, in accordance with the laws of electrolysis, kations collect at the kathode. As soon, however, as the kations at the kathode reach the “threshold number” they displace the kations from the adja- cent section of ion-proteid material; these, in turn, displace the kations from the next section, and so the wave of nega- tivity is propagated through the tissue. This view of the nature of the “wave of negativity” obtains further support from the fact that “‘the responsitivity of the kathodic points of fibres in a muscle traversed by a current increases, up to a certain limit, with the intensity of the polarising current. This limit, however, is very low . . . beyond this limit excitability diminishes, as has been shown, in _ proportion with the strength of the polarising current.’ {| Suppose a
* Gotch: Schifer’s Textbook of Physiology, vol. ii., pages 486 and 534.
+ Itid., vol. ii., page 485.
~ Biedermann: Electro-physiolozy, vol. ii., page 106
§ Ibid., vol. i,, page 98.
| Burdon Sanderson: Schifer’s Textbook of Physiciogy, vol. ii., pages 383 and 443.
“| Biedermann: Electro-physiology: Trans. by F. A. Welby, vol. i., page 285
38
certain amount of kation-proteid to be on the point of break- ing down at points which are about to be made kathodic by the polarising current, then, if the strength of the polarising current be insufficient to decompose the whole, an additional excitation will be aided by the effect already present. If, however, the polarising current has decomposed all the ion- proteid most immediately available, irritability at kathodic points will decrease.
We now touch upon the curious fact, that during the closure of a constant current, after the make twitch, no per- ceptible effect 1s usually produced in striated muscle until the current is broken. |
This depends upon two factors: the superior stimulation efficiency of rapid variation of current density (to be con- sidered later); and, secondly, the comparative exhaustion of ion-proteid material at the kathode after make. It is obvious that such exhaustion must take place sooner or later, and we need not be surprised at its taking place immediately after the initial twitch, for, as we have seen, the duration of the current has an effect upon the height of the make twitch, inasmuch as it augments it ;* that 1s to say, the constant cur- rent decomposes a large amount of ion-proteid material initially, to produce the make twitch.
We can account for the fact that persistent closure con- traction takes place more usually, and to a greater degree, in smooth than in striated muscle, by the higher value in the former of the “threshold number’—for an excess of free kations might be liberated by the current, sufficient to cause a considerable increase in tone of the muscle, and yet insuffi- cient to cause displacement, and so initiate a wave of nega- tivity. Nct only is variation of current density ordinarily of importance, but the comparative exhaustion of ion-proteid material after the make greatly increases the necessity for such variation in a way that will be explained shortly. Hence we cannot wonder that in such highly sensitive: contractile material as striated muscle persistent closure contractions are not usually seen in a marked degree.
Biedermann} states that a wave of contraction, initiated in an extra-polar tract, cannot pass the kathode of a polaris- ing current of certain intensity, while it can the anode. This is not due to the persistent closure contraction, because “‘inhi- bition is most pronounced when a persistent descending cur- rent in the upper half of the muscle has reduced the original persistent closure contraction to a minimum.” I can account
* Biedermann: Electro-physiology: Trans. by F. A. Welby, vol. i., page 176.
+ Ibid., vol i., page 296.
39
for this in the following way:—The cause of the extra-polar wave of contraction is the accompanying “wave of nega- tivity,’ which means that (in the first instance) when the wave of negativity approaches the kathode a number of kations are there set free. These kations will, however, be attract- ed by the kathode, and, moreover, there will be very little undecomposed ion-proteid from which they can displace the ions; hence, the wave of negativity will be seriously hindered, and the proteid residues at the kathode will tend to retain some of the kations. At the anode, on the contrary, unde- composed kation-proteid is abundant, and the kations are not retarded by the action of the current itself, so that the wave of negativity passes this region without hindrance.
We have seen that a certain amount of anion-proteid is present in muscle and nerve, consequently, on electrolysis taking place, anions are liberated at the anode; but, since kations are predominant, their number is not sufficient to cause displacement, and therefore a discharge; while at the kathode the proteid residues cannot take up kations, for they are immediately dissociated ; but when the passage of the cur- rent ceases, the proteid residues at cue kathode immediatuly pick up kations; hence the concentration of free kations falls at this point, and kations diffuse in from other points, in- cluding the anode; hence the mass influence of kations at the anode is diminished, the anions get the upper hand and create a discharge, which immediately, as we have seen, becomes a wave of negativity by displacement of kations. The concen- tration of kations at the physiological anode may, possibly, fall on break for other reasons ; thus some of the proteid resi- due at the kathode may, when the current is broken, take up the ions from the adjacent 1on-proteid ; this may in turn re- coup itself from the next section, and so the area of diminish- ed kation concentration would travel to the anode.
The question immediately arises: Have we any other evi- dence of the liberation of anions at the anode? The answer is that we have ample in the phenomena of electrotonus.
The effect of anions at the anode would be to lower excitability, because, iu order to obtain a sufficient excess of kations over anions to create a discharge the influence of the free anions has to be neutralised; it will be to lower con- ductivity, because the anions will tend to prevent the incom- ing kations from displacing ions from the ion-proteid by lowering their mass influence: and it will be to cause “‘posi- tivity” in the region of the anode. These are the well-known phenomena of anelectrotonus.*
* Tide Gotch: Schifer’s Textbook of Physiology, vol. ii., pages 494 and 502: and Biedermann: Electro-physiology: Trans. bv F. A. Welby, vol. 11., page 268.
40
The magnitude of the katelectrotonic effects will depend upon the magnitude of the threshold number (8). If only a part of the kations liberated at the kathode by a current is discharged, there will be improvement in excitability, con- ductivity, and “negativity” at the kathode, owing to the influence of the free kations; this will be the case when #3 is small, and occurs, as we should expect, in medullated nerve.* But where B is ‘large, and the ion-proteid therefore more stable, a very large proportion of the electrolysable portion of the ion-proteid is used up in initiating the discharge, and therefore the proteid residues at the kathode, after discharge, are great in proportion to the free kations, and their delay- ing effect neutralises the improving effect of the kations, as is the case in non-medullated nerve, where, as we have seen, 8 is greater than in medullated nerve, and there is no katelectrotonus.+. If 8 be larger still the effect of the proteid residues is to reverse the improving effect that would other- wise be produced by the kations. This is the case in muscle, as we have seen, and in muscle / is greater than in nerve. t The magnitude of the anelectrotonic effect depends on ths amount of anion-proteid, but since no anions are discharged until break it should, in general, be greater than the katelec- trotonic effect, and this is, in fact, the case.§ In further support of our theory of katelectrotonus, we may allude to the fact that with strong currents of long duration conduc- tivity is retarded at the kathode even in medullated nervell owing to the greater amount of electrolysis and the gradual diffusion of kations from the kathodic points, leaving behind the indiffusible proteid residues.
Since there is less anion-proteid than kation-proteid anelectrotonus develops more slowly than katelectrotonus, hence “currents of moderate strength but of short duration excite only on closure, 7.e., at the kathode.”{] Given the facts of electrotonus, Pfliiger’s law of contraction follows.
* Vide Gotch: Schifer’s Textbook of Physiology, vol. ii., panes “A 494 and 502; and Biedermann: Electro-physiology: Trans. A. Welby, vol. page 268.
+ Biedermann : Hh bid eae Trans. by F. A. Welby, vol. ii., page 284
t Vide section 8, this paper.
§ Biedermann: Electro-physiology: Trans. by F. A. Welby, vol. ii., page 268
|| Zbid., vol. ii., page 148. { Gotch: Schifer’s Textbook of Physiology, vol. ii., page 506.
4]
9.—Tue INFLUENCE OF VARYING CURRENT DENSITY.
It seems probable that the reason for the importance of the steepness of increase in current density for evoking sous- cular contractions les in the diffusion of the kations away from the points which form the physiological kathode. When the kations are only very slowly liberated they diffuse away from the points where they are liberated, so that they never become concentrated at any point, and their mass at any point is never appreciable in comparison with the mass of ion-proteid with which they come in contact. Hence the kations diffuse through the whole muscle without the poten- tial having risen at any point high enough to evoke a per- ceptible contraction. This view is supported by Bieder- mann’s statement that “the transmission of excitation from the seat of direct stimulation would seem, in the last resort, to be produced and conditioned by a rapid variation in the current.’’*
Persistent closure contractions, however, appear to be due to a number of kations hberated by the action of the current at the different points in the muscle forming the physiological kathode. These kations are insufficient to cause a wave of negativity from any of these points, but by raising the potential at such points they evoke a persistent contraction. If such were the case we should expect to find that persistent closure contractions were more apt to occur in muscles in which the threshold number is large; and this is the case, for “the visible manifestations of persistent excitation fall into the background, while the excitatory effects of cur- rent variation come prominently forward in proportion as the excitable protoplasm is more highly mobile,’*+ and we have seen that the less mobile a tissue is the greater is the threshold number (section 8). Thus we see why the dis- charge of the initial “wave of negativity’ tends to inhibit persistent closure contraction in striated muscle.t Only the more stable ion-proteid compounds are left at the kathode,. and these, besides being fewer in number for the current to act on, present a greater resistance to the dissociative effect of the current, so that very few ions will be liberated at any given moment, and these will diffuse into the spongioplasm before any accumulated effect is possible.
* Biedermann: Electro-physiology: Trans. by F. A. Welby, vol. i., page 193
+ Ibid., vol. i., page 192. t Vide remarks on polar excitation in muscle, section 9, this paper.
42
10.—TETANUS AND FATIGUE.
When a second momentary current is sent into a muscle before the contraction due to the first has subsided, the effect of the second current is added to that of the first, and a new contraction appears superimposed upon the old, starting from the degree of contraction at which the latter had arrived, and proceeding much as if that were the normal condition of the muscle; with succeeding currents the process goes on until a certain limit of contraction is reached, beyond which the muscle cannot go. If the shocks follow one another quickly enough the recording lever will trace upon a travel- ling surface a straight line, and the muscle is said to be in tetanus, and it will, if the shocks are kept up, continue in this condition until “fatigue” sets in, and the lever gradually sinks.
Helmholtz considered that ‘“‘from the point at which ‘te second excitation becomes effective the twitch behaves as if the contracted state of the muscle at the moment was its natural state, and the second twitch, alone, induced in ‘t” It has been found, however, that this is not true even for the second twitch; it is lower than the first and of a shorter period,* while it is obviously not applicable to the later twitches when the lmit is nearly reached. The reason for this summation is, of course, the repeated discharge of ions from the seat of stimulation. -the twitches will become smaller and smaller and shorter as the ion-proteid is used up—and no increase of contraction can then take place. At this period, however, since a great mass of kations have been rapidly liberated, they cannot diffuse at once into the spongioplasm so as to diminish the difference of potential at the contact sur- face; so that the muscle remains for some time in tetanus, and only as the kations diffuse into the spongioplasm will the lever sink and the muscle enter into “fatigue’’—-finally the lever sinks quite, and the muscle is isoelectric—or, only with the usual contact difference of potential between its hyalo- .plasmic and spongioplasmic surfaces. An objection may he raised: Why do rapidly succeeaing shocks produce reiterated contractions when a constant current fails to cause persistent contraction? There are two reasons: First, that to produce complete tetanus in striated muscle the shocks must be of extremely short duration; and we have seen that such shocks do not discharge so many ions as longer ones; that is, there is a reserve left, while the muscles in which the shocks aeed not be so short are just those in which persistent closure con-
* Biedermann: Electro-physiology: Trans. by F. A. Welby, vol. i., page 115.
43
tractions take place. Secondly, during the intervals, however short, the proteid residues will be able to gather more kations, though fewer as time goes on, because the supplies get used up ; nevertheless they will be able to do so to some extent all the time, and this corresponds to the fact that in tetanus the muscle is really vibrating, though its vibrations are imper- ceptible by ordinary methods.* This is further confirmed by the fact that too rapid a succession of stimuli corresponds in effect to a persistent stimulus, even in striated muscles.+ Schoenlein & Richet’s observations of “rhythmically interrup- ted tetanus” in striated muscles are doubtless due to the hyaloplasm reclaiming kations from the spongioplasm at the point of stimulation during the intervals. { Another reason for the rapidly decreasing height of the summated stimuli lies in the fact that the elastic re-action of the walls of the sar- cous elements becomes less and less as the muscle contracts, so that each new contraction in the series starts with less force to counteract the pull of the surface tension than the pre- vious one; hence absolute tetanus may correspond to a state of the sarcous elements in which no pull is being exerted on the wall at all. That “fatigue” is really due to the diffusion of the kations into the spongioplasm is shown by the fact that in the ureter ‘each wave of contraction produces a temporary depression of excitability and conductivity in the sheet of muscle, from which it only recovers during the subsequent diastole and interval (just as in the striated muscle-nets of insect intestine).”§ This also illustrates the rapidity with which the hyaloplasm recovers itself and again gathers kations; one is also reminded of the “refractory period” in the heart. It may be frequently observed that when a frog’s gastrocnemius has been tetanised through its nerve for as long as several minutes, so that the lever has almost dropped to the base line again through fatigue, if the tetanising current be opened only for a moment, and then closed again, the muscle, if it is fresh, will contract in tetanus almost to the same height as before. We should, indeed, expect that striated muscle with its low / (and consequently high sensi- bility), and a comparatively large surface of spongioplasm to regain kations from, would have a very much shorter “re- fractory period” than the heart or the smooth muscle of the ureter.
* Biedermann: LElectro-physiology: Trans. by F. A. Welby. i., page 135.
i
Te ONGeavol. Ie. pace TSdr. t Tbid., vol. i., page 131. § Ibid., vol. 1., page 167.
44
11.—TuHE Work or MUSCLE AND THE INFLUENCE OF TENSION.
It is well known that the work done by muscle increases, up to a certain point, with the magnitude of the load, and then decreases to zero, or even becomes negative, in contrac- tion. The reason for the initial increase in the work done, as well as the cause of the favourable effect of moderate ten- sion upon all contractile tissues, lies in the fact that the tension increases the surface of contact between the hyalo- plasm and spongioplasm. It is, indeed, obvious, @ priori, that when an elastic substance is stretched in any way its surface is increased; and this is just the case with the sarcous cle- ments. Hence, the work which has to be done against the sur- face tension, along the contact surface, in order to increase that surface, is diminished ; and, since the same work as before will be done by the ions set free on excitation, only against a tension that has been diminished, the owtput of work will be greater.
At the same time, the longitudinal stretching of the sar- cous element (spongioplasm) will have a horizontal component tending to decrease its diameter—that is, to decrease the elas- tic reaction outwards, and so decrease the tendency of the sarcous element to bulge on stimulation ; when this unfavour- able influence exactly balances the favourable, the work will be the same as with a minimal load; between these points there must be a point of maximum work output; afterwards the work falls, and, finally, becomes zero. If, now, more loading is added, when the muscle is stimulated, what hap- pens is that the pull of the hyaloplasm upon the wall of the sarcous element is diminished; normally the horizontal reac- tion would cause the walls to bulge, but now, owing to the great vertical strain, the horizontal reaction is converted into a vertical one, and the muscle elongates when it con- tracts: this is known as Weber’s paradox.* It is just as if one violently compressed an indiarubber tube which was being at the same time violently pulled. On releasing the compression the tube will become more stretched, and its aver- age bore diminished ; but, if the tube were not stretched its average bore would be increased.
12.—Tue Action oF CHEMICAL REAGENTS UPON THE CONTRACTURE OF MUSCLE. If the “negativity” at any point in a muscle is deter- mined by the number of free kations in the hyaloplasm at that point, we should expect to find that when a muscle is
* Hailiburton: Handbook of Physiology, fourth edition, page 135,
45
dipped into an electrolyte with a positive “stimulation eftici- ency’ it would become negative at those points which are wetted, and we find this to be the case. If one end of a sar- torius that is free from current is briefly immersed in highly dilute solutions of K salts, that end becomes strongly “nega- tive’ to the rest. This is simply neutralised by washing out with physiological NaCl solution.* A glance at the table of stimulation efficiencies will show that all the salts of K used in physiology have positive “‘stimulation efficiencies.” The antagonistic action of NaCl is simply accounted for by the fact that it has a negative “stimulation efficiency.” That the action of NaCl in abolishing the “negativity” induced by K salts is really due to the fact of its anions diffusing faster than its kations is shown by the fact that Engelmann found that a solution of NaCl, if stronger than 6 per cent., produces a weak “‘positivity” at points of a muscle immersed in it.; In face of the fact that nearly all potassium salts are highly positive stimuli—as shown by the table of stimula- tion efficiencies—it 1s difficult to deny that their highly poisonous effect, when applhed to muscle, must be in some way connected with the high velocity of the K ion, and I think the explanation must be this: that when a muscle is dipped into too strong a solution of KCl, suppose, the kations diffuse so rapidly into the muscle-hyaloplasm and_ spongio- plasm that little or no contraction is evoked, for the muscle is now throughly permeated with potassium ions, and ion- proteid cannot break down at any point without kations being immediately at hand to regenerate it. Even a strong cur- rent might not be able to liberate enough kations in any one section of the muscle to overcome the mass influence of those in the next; in fact, potassium salts may be said to induce a state of “‘persistent anabolism”’ in the ion-proteid. Thus it would appear that the poisonous effect of potassium salts is primarily due to loss of conductivity in the muscle, owing to an excessive rise in the threshold number, and this view is fully borne out by my experiments on the intestine of the fly. If a section of the intestine is treated, in the manner described in Section 7, with decinormal KCl solution, a block is created at the points thus treated—no contraction can pass this area, and, moreover, the peristaltic contractions travelling down the intestine do not reappear below the affected area, hence the excessive rise of the threshold num- ber at the points treated with KCl renders propagation of the wave of excitation by displacement impossible.
* Biedermann: Electro-physiologyv: Trans. by F. A. Welby,
vol. i., page 354. + Lbzd., vol. i:,. page 356.
46
It has been shown that potassium salts produce a pro- longed contraction of the gastrocnemius muscle of a frog, while calcium salts and, to a lesser extent, sodium salts, antagonise this action of potassium salts.* We can easily see that this action of potassium salts is due to the faster diffusing kation augmenting the P.D. between the hyaloplasm and spongioplasm, and hence lowering the surface tension at the contact surface, and causing prolonged contraction, while the action of the Ca salts and Na salts is simply due to the fact that in them the anion usually moves faster than the kation.
“The excitability of certain contractile substances (sper- matic filaments, ciliated cells) is considerably heightened by Na,CO, in dilute solutions.” “If the pelvic end of an uninjured curarised sartorius dips into a ‘5—1 per cent. solution of this salt, the excitability of the muscle to the closure of weak ascending currents is seen after a short time to be extraordinarily augmented, while the descending cur- rent still works quite normally, although break excitations are discharged with such low intensity of current and brief duration of closure as would not occur in normal muscle.’’t This improvement of contraction and excitability on treating with the Na,CO, is, I believe, owing to its low positive stimulation efficiency shghtly increasing the threshold num- ber, while the incoming kations enable a sufficient number to cause displacement to gather more quickly at any point. In my own experiments I have observed this improvement in the sartorious, in the semi-membranosus of the frog (fig. 7), and in the intestine of the fly. If a section of the fly’s intestine be touched with decinormal Na,CO,, the peristaltic contrac- tions are much augmented at that part; and, if the intestine be quiescent owing to long exposure to NaCl, peristaltic contractions will start at the point painted with Na,CQO,. The improvement, in both cases, quickly dies away, and the intestine becomes puckered at the part affected owing to increase of tone, this part now acting as if it had been painted with KCl. This is to be explained by the effect of the natrions being, at first, partly neutralised by the chlori- dions already present, and then as the natrions become pre- dominant the stimulation efficiency is too great, and the ion- proteids enter into persistent anabolism.
*W. D. Zoethout: American Journal of Physiology, May, Ne : The Effects of Potassium and Calcium Ions on Striated Luscle.
+ Biedermann: Electro-physiology: Trans. by F. A. Welby, vol. 1., page 221.
47
Seu ven £4 WARTS Ke :
FIGURE 7.
13.—RHYTHMICITY IN MUSCLE AND THE ACTION OF INHIBITORY AND AUGMENTOR NERVES.
Direct proof that the rhythm of the heart is due to the presence of electrolytes in the circulating medium is afforded by the fact tuat if the proteids be removed from serum which is then circulated through the heart the rhythmic contractions will continue. If the salts are removed and the serum is circulated it is ineffective.* The solutions generally used aud found effective stimuli for the heart-beat have negative stimu- lation efficiencies, owing to the predominance of NaCl. Let us, therefore, consider the case of an excised heart through which a solution, which has a negative stimulation efficiency, is circulated. Assuming that the walls of the heart are equally permeable to both the ions in the solution— an assumption which, however, is not strictly permissible— we see that, owing to the difference of ionic concentration on the two sides of the muscle surface, ions are continually diffusing in—but at different rates—the anions more quickly than the kations. Since the time taken for the anions enter- ing the hyaloplasm to reach a given number—the threshold number—will be inversely proportional to the velocity with which the anions enter, we may conclude that, other things being equal, the frequency of the beat is creater the greater the velocity of the anions in the solution. Also, since the driving force which causes the ions to diffuse into the muscle is dependent upon the difference in ionic concentrations on the two sides of the muscle surface, we see that, if the solu-
* Gaskell : a ee Textbook ioe Pieeaee a te DRE 226.
48
tion is-kept sufficiently dilute to ensure complete dissociation of the salts, the frequency of the beat will be greater the greater the concentration. And, obviously, the frequency will be less the vreater the threshold number.
We further notice that if the ions diffusing into the muscle gathered unchecked on the muscle side of the sur- face, diffusion would shortly cease because of the approxi- mation of the concentrations on both sides—the process could not be kept up. But we know that this is not the case; a periodic discharge of anions takes place which, by releasing kations, starts waves of negativity, giving rise to the contrac- tions, or, when the heart is bathed in a solution with a posi- tive stimulation efficiency, the periodic discharge is one of kations starting, as before, a wave of negativity. The con- centration after each contraction is, therefore, on the muscle side, kept automatically constant, as far as anions are con- cerned ; on the fluid side it is kept absolutely constant by cir- culation, but during the intervals between contractions the difference between the concentrations on the two sides is not constant, but continually falls off. Another fact to be con- sidered is that the difference between the velocities of en- trance of the anions and kations will diminish progressively during the intervals between contractions owing to the electro- static repulsion, due to the excess of one kind of ion which has entered, tending to accelerate the other kind of ion and retard the ion bearing a similar charge. Finally, we have to take into account the reciprocal influence of kations and anions in altering the threshold number—kations will aug- ment the threshold number for anions, and anions will aug- ment the threshold number for kations. Hence the threshold number will be greater the less the difference be- tween the velocities of the anions and kations on entering the muscle. Also, it is possible that kations of one kind may raise the threshold number for kations of another kind (when the solution contains two or more salts). Hence the threshold number, and consequently the extent of contraction, will vary considerably in different solutions.
It is obvious that a number of conditions must be satis- fied in order that a solution may be able to keep a heart beat- ing. Thus, the threshold number must be reached on the muscle side by the faster-moving ions before their velocity has been reduced to that of the slower-moving ions, by the electrostatic force which they develop on the muscle side. This involves the difference between the velocities of the anions and kations, the influence of one sort of ion in rais- ing the threshold number for another sort, and the difference between the concentrations of the ions on the two sides of the muscle. Then, again, if the frequency of the beat is too
EE EE
49
great the beats will merge into one another, and the heart will go into tonic contraction.
Thus, the normal rhythm of the heart is due to the ions diffusing in from the blood, and the delicate adjustment of the threshold number to the nature and concentration of the salts in the blood. Almost any point in the heart is capable, in a greater or less degree, of initiating this rhythm, ¢.g., if the auriculo-ventricular groove be ligatured or cut through, a series of rhythmical contractions is initiated; this is soon suppressed ; subsequently a more permanent series is initi- ated.* The “rhythm of excitation” is due to the kations re- leased by the injury due to the cut or ligature, the “rhythm of development” to kations diffusing in from capillary spaces.
A permanent rhythm, such as we see in the normal heart, could not be maintained on a nutrient fluid whose stimulation efficiency was negative, unless the excess of anions was continually removed, for otherwise the anions would gradually convert most of the kation-proteid into anion-proteid, and contraction would become impossible. The solutions, however, which are generally used as circulating media to keep up the heartbeat have negative stimulation efficiencies owing to the predominance of NaCl. We should, therefore, expect to find, if the preceding reasoning has been correct, that the rhythm of the heart would be slowed by add- ing a little KCl to the solution (sufficient to reduce its stimulation efficiency without making it positive), and quick- ened by adding CaCl, so as to increase its stimulation efh- ciency (since CaCl, has a greater stimulation efficiency than NaCl.). This was found to be the case by Greene.t He found that calcium salts in isotonic solutions of NaCl stimu- lated a cardiac strip to increased rhythm and final permaneat contracture. KCl in isotonic solutions of NaCl prevent- ed contractions and kept the ventricular strip in a state of relaxation. If the salts CaCl, and KCl were in the pro- portions of ‘026 per cent. CaCl, to -03 per cent. KCl, a few good contractions at a very slow and irregular rate might result. If the ratio was changed by increasing the CaCl,, or by decreasing the KCl, then the contractions were in- creased in frequency; but if the CaCl, was diminished or KCI increased, few contractions were developed, or none at allt At first sight, these results might seem to be opposed
; * Gaskell: Schifer’s Textbook of Physiology, vol. ii., page fv.
+ C. W. Greene: American Journal of Physiology, 1899, vol. ii., page 82. +t Ibid., vol. ii., pages 107 and 125.
50
to those obtained by Zoethout in experiments on the gastroc- nemius,* but, in reality, these results are due to the action of KCl and CaCl, in lowering and raising the stimulation efficiency of NaCl respectively. Pure CaCl, or KCl applied to a heart strip throws it into strong tone,{ as might be expected from the high stimulation efficiency of both, since the frequency of contraction is greater the greater the difference between the ionic velocities. Hence the two sets of results are, by this theory, brought into entire harmony.
With regard to the influence of the threshold number in lowering the rate of rhythm, it is obvious that the height of contraction depends upon the magnitude of the threshold number, for the greater the potential of the wave of negativity the greater is the maximum P.D. produced between the hyaloplasm and spongioplasm; hence we should expect that the slower the rhythm the greater the height of contraction, other things being equal. This has been experimentally proved for smooth muscle by Woodworth.{ As P grows greater in excitable tissues we find that the “refractory period” grows greater. During this period the tissue will not respond to stimuli, and it is greater in cardiac than in _ striated skeletal muscle.§ The reason is that, 6 being greater, a greater time must be allowed for the amount of ion-proteid corresponding to 6 to become unstable ; of course, the moment at which the kations at the point of initiation are sufficient to cause a contraction will coincide with the moment at which the ion-proteid is in a certain minimal state of instability. This is the same as saying that immediately after a wave of negativity has passed a point, 6 is great at that point, and the amount of decomposable material small; the amount of decomposable material grows, and £ diminishes until a cer- tain point is reached at which excitation by a given stimulus is possible. Thus the slowing of a wave of negativity travel- ling too soon after a contraction is due to the greater magni- tude of the threshold number.|| Since the frequency of contraction is greater the greater the difference between the ionic velocities, any solution in which the ions move at very different rates will cause tonic contraction. Hence alkalies cause tonic contraction.{]
* Vide section 12.
+C. W. Greene: American Journal of Physiology, 1899, vol. ii., page 101.
t R. S. Woodworth: American Journal of Physiology, 1899. a § Gaskell: Schafer’s Textbonk of Physiology. vol. ii., page 189,
|| Ibid., vol. i1., page 195.
q Ibid., vol. ii., page 195.
51
In general, inhibition must be due to an income of anions large enough to neutralise the kations present, but not strong enough to cause a discharge in addi- tion. If inhibition in the heart were due to the refractory period after a subminimal discharge of kations it could not last 252 seconds after stimulation of the vagus, as it may do.* We should expect the anions to cause a relaxation, and this takes place.t | We should expect excitation of the inhibitory nerve, if it sets free anions in the muscle, to cause ‘‘positi- vity” at the points affected, and this is the case.t{ All doubt as to the action of the inhibitory fibres of the vagus being comparable to the effect of free anions at the parts affected— that is, to anelectrotonus—is removed by the fact that “‘a crystal of salt applied to the sinus will produce une same electrical variation as stimulation of the vagus nerve,” § since in NaCl the stimulation efficiency is negative. In some animals the contractions of the ventricle are not diminished by vagus stimulation, hence there must be few or no anions at the vagus nerve-endings in the ventricles of these animals, and a most remarkable confirmation of my theory as to the nature of the “‘staircase’’|| and of inhibition is that “‘another somewhat unexpected coincidence is brought out by the com- parison of ventricular muscle, whose contractions are diminished by vagus’ stimulation and __ ventricular muscle, whose contractions are not so diminished, namely, that the staircase phenomenon obtains only in the former case, and not in the latter.” {] The effect of the anions liberated by the inhibitory nerve in the heart will be to depress the rate of the contractions, because a greater number of kations will have to gather at each point to over- come the mass influence of the anions. To depress the con- ductivity owing to the state of anelectrotonus induced, and to diminish the force of contractions owing to the diminished tonicity: all these are known effects of stimulation of the inhibitory nerve. ** The auriculo-ventricular ring always specially tends to block contractions—we may assume that
* Gaskell: Schiifer’s Textbook of Physiology, vol. ii., page
207 t Ibid., page 210.
+
t Biedermann: Electro-physiology, vol. ii., page 257. me § Gaskell: Schiafer’s Textbook of Physiology, vol. ii., page
|| Vide section 7, this paper.
{ Gaskell: Schifer’s Textbook of Physiology, vol. 11., page 214.
** Tbid., vol. ii., page 209.
52
this is due to an abundance of anions in this part—hence if we cut off the supply of kations, by hgaturing the coronary arteries, a block takes place,* because the anions have now got the upper hand.
The augmentor nerves increase the rate of rhythm, be- cause kations are more abundant, and therefore at the initial points of contraction they more quickly reach the threshold number. The force of contractions increases because of in- creased tonicity. Conductivity increases because the inhibi- tory action of the anion-proteid normally present is overcome by the free kations; that is, presuming that the augmentor nerves end in spots where anion-proteid is scarce, and that the impulse therefore sets free kations; and all these are known effects of stimulating the augmentor nerve fibres.t The alteration in tone and the negative variation produced by stimulating the augmentor fibres is slight. { This is to be expected, otherwise a discharge would be initiated at the nerve endings, and the refractory period would diminish con- ductivity. The discharge by the augmentor fibres must be less than the threshold number.
The after-effect of inhibitory nerves in improying con- ductivity § is probably due to increased instability of the jon- proteid, the after-effect of the augmentors to the reverse.
The facts we have considered throw light on the whole action of antagonistic nerves in the many cases where there is a double nerve supply.
14.—RHYTHMICITY IN NERVES.
One of the best examples of rhythmicity in nerves is that of Ritter’s opening tetanus. ‘An indirectly excited muscle may, after prolonged closure of a powerful battery current, fall, on breaking the circuit, into a state of persistent tetanic excitation.” || It specially occurs in “cooled frogs,” when, as we saw in section 7, the threshold number is great, and the nervous impulse which gives rise to the tetanus is rhythmic.{] There can be little doubt that this is a rhythmic discharge due to a collection of anions at the anode, just as a rhythmic
* Gaskell: Schifer’s Textbook of Physiology, vol. i1., page 193.
+ Ibid., vol. ii., page 216.
+ Ibid., vol. ii., page 218,
§ Ibid., vol, ii., page 220.
| Biedermann: Electro-physiology: Trans. by F. A. Welby, vol. ii., page 117.
q Ibid., vol. ii., page 119.
53
discharge is caused in the heart by the anions in a circulating fluid. ‘Che long closure of a powerful current allows plenty of time for a large number of anions to be liberated at the anode, and, what is more important, a large amount of kation- proteid to be decomposed at the kathode, so that although the excess of anions liberated at the anode may not be equal to the threshold number’ while the current is closed, yet, on opening, the sudden rush of kations to the former kathode causes a sudden fall in the value of the threshold number, for anions, at the anode, so that the num- ber of free anions may now be many times the value of the threshold number. The fact that it occurs best when the threshold number is great (cooled nerves)—when the decom- position at the kathode is most marked*—favours this view. The fact that the “opening tetanus” is removed by 1mmer- sion of the nerve in KNO, shows that it is due to anions, since it 1s removed by an excess of kations.
15.—THE MovEMENTS OF PLANTS.
This theory of the influence of the ion-proteid upon the surface tension of protoplasm gives a simple explanation of the movements, and especially the heliotropism, of plants. It is a well-known fact that, in the presence of chlorophyll, green plants, under the influence of light, decompose carbon dioxide, retaining the carbon and_ giving off the oxygen — this carbon is built up into carbo-hydrates and _ proteid. + Hence, it is evident that *''the rapidity with which the synthesis of proteid (and therefore of ion-proteid) goes on is dependent upon the supply of carbon; that is, upon the presence and intensity of illumination. Supposing ‘a contact difference of potential, due to free ions, exists between the protoplasm of plant cells and the cell walls, it is readily seen that at the point where the assimilation of free ions into ion-proteid is going on most rapidly, this contact difference of potential will be diminished, and therefore, as we have repeatedly pointed out, the surface tension along the contact surface will be increased. This will mean decrease of surface at such points, and comparative in- crease of surface at other points; therefore, a cylindrical stem, in which assimilation 1s going on more rapidly on one side than on the other, will bend towards the former side.
But, we have seen that if one side of a crowing plant stem is more strongly illuminated than the other, assimilation will be going on more quickly on the illuminated side; there-
—
* Vide discussion of electrotonus, this paper, section 8. + Vide Vine’s Physiology of Plants, 1886, pages 140-148.
54
fore, we should expect growing plants, with slender mobile stems, to bend towards the light. And such is, in fact, the case. [I quote from Darwin: The Movements of Plants, page 465:—“In our various experiments we were often struck with the accuracy with which seedlings pointed to a light, although of small size. To test this, many seedlings of Phalaris, which had germinated in darkness in a very nar- row box several feet in length, were placed in a darkened room near to and in front of a lamp bearing a small cylindri- cal wick. The cotyledons at the two ends and in the central part of the box would, therefore, have to bend in widely different directions in order to point to the light. After they had become rectangularly bent, a long white thread was stretched by two persons, close over and parallel, first to one and then to another cotyledon; and the thread was found in almost every case actually to intersect the small circular wick of the now extinguished lamp. The deviation from accuracy never exceeded, as far as we could judge, a degree or two.”
Of course, in such cases, it may be objected that chloro- phyll is not yet fully formed ; but, inasmuch as chlorophyll is very quickly developed in the light, it may be supposed that the process of its formation, and the consequent accelerated synthesis of proteid, begins at once; while plenty of time was allowed for the reaction, since, in the experiment just before the one quoted, eight hours was allowed for seedlings of Brassica and Phalaris to bend “rectangularly towards the light.”
: In order to see how intimately the bendine of plants towards the hght depends upon the illumination of the chlorophyll, it is only necessary to refer to Darwin’s “Move- ments of Plants,” page 449 to page 468.
The few exceptions nearly all admit of some other expla- nation. Thus, Darwin shows that heliotropism may be much modified in some plants owing to their habit of climbing; in other cases apheliotropism may be induced because too intense illumination injures the chlorophyll,* and therefore reverses the effect we have described. Further, in time, the prepon- derating growth of the illuminated side will tend to reverse the effect. In the rare cases where plants containing little or no chlorophyll are heliotropic we may assume that light aids assimilation in some other way. The tendency for leaves to place themselves perpendicular to any not too strong illumi- nation} is easily understood when we consider the influence of illumination upon the leaf stalk; illumination of its upper surface will cause a diminution of that surface—as we have
* Darwin: The Movements of Plants, page 446.
+ Ibid., page 449.
. .
a9)
seen—and this will counteract the effect of gravity tending to make the leaf hang downwards.
The importance of sudden change in illumination*® is due to two factors: one the tendency of growth to counteract helotropism if illumination is carried on for some time, and the other the tendency the ions from the unilluminated side will have to diffuse faster into the illuminated side, as the ions there are assimilated, a tendency which would slichtly increase the P.D. at first lowered by the assimilation. It is evident that in normal growing plants these factors of heliotropism, growth, gravity, etc., will eventually reach a state of more or less settled equilibrium, which will determine the permanent form of woody parts.
That differences of potential, such as we have described, do exist in plants is well known. Thus, Biedermann] men- tions that Kunkel found the veins of a leaf “‘positive” to the greea surface (translating this physiological terminology this means that internally to the leaf there was an E.M.F. tend- ing to promote a current from the green parts to the veins), There can be no doubt, I think, that this is due to the katious of the salts, brought up by the transpiration current, diffusing more rapidly through the walls of the vessels in the veins than the anions. The salts brought up are mainly KNO, and KCl, in which the kation has a greater velocity than the anion.{ The same explanation apples to the “negativity” of the roots of a seedling towards the cotyledon, and higher parts,§ for the roots would have a large supply of kations due to diffusion from the moisture in the soil which diminishes progressively as the transpiration current mounts up the stem and the kations are assimilated.
Hermann|| found that cross sections of the stem of a plant were “negative” to normal parts. This is doubtless due to decomposition of kation-proteid at the point of injury liberating kations.
Burdon-Sanderson finds that when the leaf of Dionea closes, the lower surface becomes “negative” to the upper. This affords an explanation of its closure, since kations are liberated on the under side the surface tension on that side is
* Darwin: The Movements of Plants, page 457. + Biedermann: Electro-physiology: Trans. by F. A. Welby, vol. 11., page 2.
+ Vide Table of Stimulation Efficiencies, this paper, sec- tion 3.
§ Biedermann: Electro-physiology: Trans. by F. A. Welby, vol. ii., page 5 | Ibid., vol. 11., page 2.
q Ibid., vol. ii.. page 23.
56
reduced ; that is, the under surface tends to increase; and the upper to decrease, hence the leaf closes.
16.—SuMMARY.
It has been proved by Loeb and others that proteid takes up ions to form a loose compound, which they call ion- prc teid.
Since these ion-proteid molecules must always be break- ing down, tnere must be, for this reason, if not for others, a number of free ions in any protoplasmic body, and therefore, in general, a difference of potential between it and the medium in which it lives.
1t is acknowledged by many physiologists* that the movements of unicellular organisms are due to changes in surface tension, while others, as Schafer,; consider it pro- bable that the movements of muscles may ‘be due to the same cause. It is, indeed, obvious from the structure of amceba, cilia, muscle, etc., that, if changes in surface tension take place, movements must follow.
But since, for obvious reasons, the number of free ions in a protoplasmic body must always be chaneing or subject to change, 1t follows from known physical laws that the sur- face tension must also change.
We have shown that this mode of accounting for the movements of organisms enables us to explain the galvano- taxis and chemotaxis ot unicellular organisms—the contrac- tion of muscle—the electro-motive and other phenomena ac- companying muscular contraction and the nervous impulse— the rhythmicity of certain muscles and nerves and the variations in their rhythm—the action of inhibitory and augmentor nerves, and the movements and electro-motive phe- nomena of plants.
It seems, therefore, certain that this explanation of the genesis of movement in living bodies is, in the main, true, and that it is probably capable of explaining the whole of thai vast complex of facts which have been gathered together under the head of phenomena of contractility and irritability.
* Vide Biitschli : Protopiies ded Midtbscopte Raat! “Pie, by E. A. Minchin, 1894, page 289: and Verworn: General Physiology: Trans. by Frederic 8. Lee, page 561,
+ Schifer: Essentials of Histology, sixth edition, page 56.
57
GEOLOGICAL REPORT’ ON THE COUNTRY TRAVERSED BY THE SOUTH AUSTRALIAN GOVERNMENT NORTH-WEST PROSPECTING EXPEDITION, 1903.
By Herrsert Basepow, Prospector to the Expedition.
[Read October 4, 1904.] Prates XITI. to XX,
CoNnTENTS. Pre-Cambrian: The Ranges of North-Western South Australie... 57 Musgrave Ranges and their Outliers ... snip) Mann Ranges and their Outliers —... ae Oo Tomkinson Ranges $i sin sy! bee > Everard Ranges ... : se Pata Br,
Ayers Ranges, Northern Peeritory sash Scanpat
The Indulkana Outcrop ty ete We teem &: Cambrian :—
The Head of Lake Torrens ... ves sa eon Ordovician :—
The Mount Chandler Outecrop son oe eg eee
Mount Conner ... ue se eS
The Mount Kingston Outer —_ = sapueet
Mount Olga and Ayers Rock a S abe Se) Supra-Cretaceous :—
The Desert Sandstone ore ee pf SSO Recent Surface Deposits, Sandhills, ete. ee ... 89 Appendix :—
Petrological Notes on Rocks collected during the
Expedition Abe ay xii Bk oe ner |
Tur RancGes or NortTH-WESTERN SoutH AUSTRALIA.
Although maps represent these ranges as separate en- tities, they must, on geological and lithological grounds, be regarded as belonging to one and the same grand system, the intervening tracts of country which now separate the indi- vidual ranges being, for the most part, superficial deposits of comparatively recent sands and sandhills, or supra-creta- ceous deposits, known as the “desert sandstone.”
Rising abruptly + from the surrounding sandy country,
* This paper, which has been slightly abridged, was the suc- cessful Tate Memorial Medal Thesis, 1904.
+ Compare J. Forrest, Explorations in Australia, III., page 248 :—‘‘The whole country is level, the ranges rising abruptly out of the plains, . »” Also the general statement by James Geikie, in Earth Sculpture. page 202 - “Rising boldly above the general level, they exhibit no trace of talus or debris. 2?
58
they extend in an easterly and westerly direction as huge, in- trusive masses within crystalline schists and gneisses, mostly devoid of vegetation, though the intruded rocks bear “mulga,’ pine tree, and undergrowth of bush and grass. Fertile sandy loams, carrying mulga scrub of variable extent, surround them; while beyond this belt sandhills with “porcu- pine grass,” “desert oak,” “‘quondong,” etc., prevail.
Their main bulk consists of plutonic masses, which form the cores of anticlinal folds of metamorphic rocks. Owing to the intense metamorphism induced not only in the in- truded rocks, but also at the outskirts of the igneous intru- sions themselves, it is often impossible to determine the actual plane of contact.* This factor has further been the cause of the contact rocks assuming a distinctive character by re-crystallisation of the original constituents (/ornfelsstruc tur). In this process the production of epidote has been greater than that of all other minerals, it being by far the most generally distributed near intrusions.
The following section is a diagrammatic representation of the mode of occurrence of the igneous and metamorphic series.
Fig. 1.—DI1aAGRAMMATIC SECTION THROUGH PORTION OF THE Musgrave Ranges, East or MircHey’s Knos.
Owing to the absence of representatives of the Cambrian system in proximity to the ranges, the age of the igneous in- trusions could not be definitely determined, but they cer- tainly took place before the Ordovician period, as examples may be seen in the low-lying outskirts, as, for instance, Indulkana, of rocks of the Ordovician period overlying the intruded fundamentals, and not being themselves penetrated by the eruptives.
The Musgrave Ranges comprise an extensive series, rang- ing from acid to basic; the Mann principally acid and inter-
™ Mons. Michél-Levy has described similar features in the gneisses of the Central Plateau of France. He points out that whenever it is the case that the granite is massive and intrudes rocks of acid character the plane of contact is not sharp, but the intruded and intrusive rocks are connected by a contact zone.—- Bull. Soe. Géol., France, Ser. 3, tome vii. pages 852 et 853.
59
mediate; while in the Tomkinson Ranges members of the basic and intermediate families are typical. The intermediate group is represented throughout by numerous diorite dykes, which are usually of no great thickness, but their frequent appearance within short distances of one another is in cases marked. Their plane of contact with the intruded rock is always well defined.* |The diorite intrusions have occurred later than the main granitic injections of the dis- trict. This is evident from the fact that often the diorite can be found penetrating the granite.t Yet the diorite in places does not appear to have been much subsequent in time, for magmatic intergrowths may be observed between diorite and granite rock that have been produced during a state of semi-plasticity of the latter. On the other hand, magmatic inclusions of granite rock within the diorite occur. These have been torn from the walls of the fissure, into which the diorite was injected, and embedded in the mass.
The intruded rocks, where they appear in considerable and persistent thickness (Mdchtigkeit), may be included generally under the headings of “gneissic quartzite’ { or “gneiss” proper ; yet other crystalline schists are not wanting, although they are not represented to the same extent. The great variations in readings of the compass needle, produced by the magnetic minerals contained in the different granitic rocks that compose these ranges, have already been noted by various explorers.
THe MuSGRAVE RANGES.
General Remarks.—The Musgrave Ranges (Gosse, 1873) lie almost wholly in the State of South Australia, only two minor offshoots passing northward to beyond the boundary, in the localities of Opparinna and Fraser Hill. They rise from the plains as a compact chain that continues in an easterly and ‘westerly direction for a distance of over one hundred miles. They are, however, cut in several places by valleys of denudation that are now occupied by vast deposits of sand, the upper surfaces of which form elevated plains (such as Glen Ferdinand), that permit the ranges being crossed with no great difficulty transversely to their long axis. Their breadth varies, the maximum being about thirty-five miles,
* Compare Michél-Levy, op. cit., pages 845 et 872.
t See also H. Y. L. Brown, Report Journey from Warrina to Musgrave Ranges, page 2 (Adelaide: by authority, 1889) ; and V. Streich, Scien, Res. Elder Expl. Exp., Trans. Roy. Soc., S.A., vol. xvi., pp. 77 and 83.
{ An altered (clastic) sandstone in which only a very faint indication of foliation has been brought about by the production of secondary minerals.
60
and the altitude is considerable. Mount Woodroffe, the highest peak, is estimated to be over 5,000 feet above sea level, and more than 3,000 feet above the level of the adjoin- ing desert. Hence this chain of mountains is by far the most massive of the series seen during the expedition.
Igneous intrusions on a grand scale have produced the upheaval and form the inner mass of the several folds into which the intruded metamorphic beds have been thrown.
Mr. W. C. Gosse, in 1874, pointe] out that the Mus- grave Ranges “are composed chiefly of granite,”* and later Mr. H. Y. L. Brown’y’ (1889) that they “are composed of eruptive granite and metamorphic granite rocks of various
kinds, chiefly hornblendic, and seldom containing mica,” :
comprising “ordinary granite, porphyritic granite, horn- blendic granite, graphic granite, granulite, pegmatite, syenite, quartz syenite, and epidosite, gneiss, both hern- blendic and micaceous, and siliceous and felspathic crystal- line rocks of various kinds,” diorite and _ dolerite. Mr. J. Carruthers stated: — ;“The Musgrave Ranges are composed principally of red granite rocks, and covered with spinifex and few scattered pines; the flats between the hills, which are principally formed by large creeks coming out of the ranges, are beautifully grassed, . . . the soils being a rich, red, sandy alluvial, and firm red loam.”
Igneous Rocks.—The intrusives vary in character from highly acidic to basic, the differences, however, between the members of one and the same family being slight. The acid rocks are principally granitic, the greater bulk consisting of a rather coarse-grained porphyritic variety, with large cor- roded crystals of a bluish felspar (orthoclase). Ernest Giles was the first to mentions this type of granite, and assigned to it the expressive term of “granite-conglomerate,” making thereby particular reference to Mount Carnarvon, which is the eastern hmit of the Musgrave Ranges. Mr. W. C. Gosse, moreover, in describing Mount Morris, wrote|| “that this portion of the range is composed of very coarse granite. At the entrance to Jacky’s Pass, on the south, this class of granite flanks the chain, but further east the southern slopes
* Parliamentary Paper, No, 48, House Assembly, page 18.
+ Report on Journey from Warrina to Musgrave Ranges. By authority: 1889,
1 Report to Surveyor General (Adelaide Observer, January 16, 1892).
§ Geogr. Travels in Centr. Austr., 1872-1873, Part ii., page 84.
| Parliamentary Paper, No, 48, House Assembly, 1874, page 16.
and that they are intruded by
61
consist of fine-grained gneiss, the granitic outcrops being in the heart of the range. The main intrusion thus extends east of the pass towards Mount Woodroffe, thence taking a more northerly turn in direction of Mount Carnarvon; it has its greatest development east of Harries’ Spring, while on the eastern borders of the range gneisses predominate. In this respect the Musgrave resemble the Mann Ranges
A subsidiary arm of the main injection of the igneous rock produces a prominence in the neighbourhood of Mit- chell’s Knob, the major and minor veins of the same enclosing clastic (?) gneisses. (See fig. 1.)
The ranges on the northern flanks, north of Mount Fer- dinand, present a picturesque appearance, produced by gro- tesquely shaped, isolated, bare, granitic masses (Sekunddre Kuppen).
The granite, particularly that of the porphyritic variety, is characterised in the field by its strong tendency towards concentric weathering, large shells of rock exfoliating con- centrically to the present contour of the rock surface. This feature is deserving of particular notice.
In the valley of the Ferdinand, west of the mount bear- ing a similar name, the character of the granite changes to a more even-grained, white variety, with irregular aggregates of hornblende and biotite distributed through its mass. Where this granite has been cut by diorite the contact is marked by a development of large idiomorphic crystals of hornblende. In the same locality minor veins of epidote granite, with a red orthoclase felspar, and graphic granite traverse the main granitic mass in a westerly course.
East of Lungley’s Gully an intrusion of red aplite is deli- cately veined with crystalline epidote, and the planes of slick- ensiding, that cut the rock, are lined with a “‘harnish” of secondary mica and rhombohedral calcite. The rock is con- spicuously jointed in two planes, the first of which strikes W., 20° N., and dips northerly 73°, the second striking N., 45° E., and dipping 23° S.E.; a third plane is less regu- lar. Rocks belonging to the peridotite family were found in the form of pebbles among the wash of a small watercourse south of Mount Morris, but the rock was not observed in situ. Diorite dykes are very plentiful. The diorite rock is vormai, quartzless, and moderately fine-grained. It is usuaily mica- ceous. Dolerite dykes are less numerous. They cousist of a finely crystalline groundmass with porphyritic crystals of felspar and pseudomorphous (?) epidote. Dykes of a peculiar voleanic rock are rare. Fluidal structure is typical when viewed under the microscope, it being marked by ores
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of iron in a glassy groundmass. Corroded phenocrysts of olivine are plentiful.
Metamorphic Rocks.—The gneisses of the Musgrave Ranges, derived both from the alteration of sedimentary and igneous rocks, with few exceptions, skirt the chain on either side ; they also form the intermediate flanks of folds produced by the intrusion of the eruptives. They do not extend to the same altitude as the igneous rocks, and, as is the case in the Mann Ranges, they appear more extensive on the eastern than on the western limits of the range.
A natural section along the course of Whittell’s Creek presented a variety of schists within small range of country. The section showed a gradation from a compact gneiss through a series of beds, as follows: —Quartzite, quartz schist (lami- nated), schists of various kinds (mica, chlorite, epidote, and garnetiferous, with numerous perfect dodecahedral crystals of garnet in a dark. quartzitic, schistose matrix); thence quartzite, jointed regularly in two directions at right angles. The strike varies from almost due north and south to east and west ; the latter is, however, the general strike of the beds of this section. East of Mount Woodward the gneisses are in parts compact, in parts fissile. They are jointed vertically in - direction north, few degrees east, and at right angles to this plane. The planes of foliation dip south. North of here it is distinctly granitic in character, and separated into more or less horizontal (lenticular) layers by planes of division ; these layers thickening appreciably as the depth increases (Bank- formige Absonderung). At the contact with a diorite dyke it has assumed a remarkable, closely foliated character; the folia, produced by a very dark coloured biotite and stringlets of quartz running parallel with the direction of intrusion.
The gorge cut by the Opparinna Creek affords another section within the gneisses that skirt the watercourse in the form of scarped, shattered walls. They show signs of earth - movement and folding, and are replaced in parts by smaller bands of chloritic and_sericite schists, often traversed by small seams of epidote at the zone of con- tact with diorite dykes. At Opparinna Spring the country consists of a compact, dark bluish-black gneiss, vertically jointed in directions W., 20° N., and N., 10° E. (less per- fectly), and in planes dipping 8S. 5°. Along the last-men- tioned plane the rock parts readily into layers about twelve inches thick. North of the spring the metamorphic series changes to a compact brown gneiss, weathering massive granitic, and showing a regular cubic jointing. The texture, in parts, approaches the “graphic” intergrowth of some granites, the quartz occurring as rounded and elongated inclusions
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(quartz de corrosion) in the felspar.* The optically-continu- ous character of the quartz and felspar can readily be detected in hand specimens by suitably reflecting the light from a freshly fractured surface. The planes of foliation of the true gneiss strike W., 20° 8., and dip northerly 11°.
South of Opparinna Spring the gneissic quartzites | com- posing the ranges are thrown into a great overthrust fold which can be observed on the eastern face of the gorge cut by Moffat Creek, by following up the exposure of two pro- minent parallel layers of the rock. These, on the south, dip at a low angle of about 30°, and on the north the same bands are seen dipping in the same direction at a high angle, with an inward curve at the top. The crest of the fold has been removed by denudation; yet the outline of the original con- tortion of the beds, upon reconstruction, was evidently as represented in the figure. Within the fold exists a zone of extensive dioritic intrusion, while the country is severely frac- tured.
Fig. 2.—An OvertHrust Foip 1n BEps oF GNEISSIC QUARTZITE. Morrat CREEK, SoutH OF OPPARINNA SPRING, MusGRAVE RANGES.
A similar feature, though on a smaller scale, was en- countered in Jacky’s Pass. Beds of gneiss are in this case bent to a considerable degree; a diorite intrusion within the fold accompanied the earth-movement.
Several island-like masses of gneiss rise above the sands to the west and south-west of the group of hills termed the Kelly Hills. One of such occurs close to a native soakage
* Lacroix has described a somewhat similar type of gneiss ey eon India.—Record Geol. Survey, India, xxiv., page
+t No doubt equivalent to the ‘‘granitoid quartzites”’ of this
locality mentioned by R. W. ay Extracts Journals of Ex- plorations, by R. T. Maurice (by authority: 1904, page 29).
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well, known to the natives as Tarrawaitarratarra, and it has been conditioned by the intrusion, within a series of schists, of pegmatite and greisen. The muscovite of the pegmatite is remarkable for its peculiar reddish-violet tint, closely re- sembling that of lepidolite, but failing to give the character- istic flame test of the latter. The mica, moreover, of one of the schists is similar to that of the true igneous rock, though it occurs as smaller individuals. The schist is usually a closely laminated, quartz-mica rock, often “knotted” oy secondary mineral development; while at the contact with a diorite dyke on the summit of the hill a finely foliated gneiss has been produced. The planes of schistosity strike N., 12° E., and dip 40° E. The height above sea level of the expos- ure is 2,100 feet, and it stands 140 feet above the sand plains. The beds have suffered local displacements; planes of shear are thickly lined with a glossy layer of secondary minerals.
Outcrops some miles to the north of this exposure were presumably observed to be overlaid by conspicuous beds of quartzite. Opportunity was not afforded to determine whe- ther these beds form part of the fundamental series or whe- ther they are unconformable to the schists.
The hills further south are composed of rock of the com- pact granitic character already discussed. In parts they are of the “fluxion” type of gneiss, and they are characterised by weathering concentrically.
OUTLIERS OF THE MuSGRAVE RANGES.
The Musgrave Ranges are bordered on the south by humerous outliers of granitic rock, many of which are of considerable magnitude, and have consequently received separate names. A few of these outliers will be briefly discussed : — 7
Mount Caroline.—South of that portion of the Mus- grave Ranges known as Lungley’s Gully, about eight miles, stands a bold, isolated mount, over 1,000 feet above the level of the sands. It is known as Mount Caroline. Its mass is composed of biotite granite, with a slight tendency to folia- tion on the part of the mica. Large porphyritic, corroded crystals of orthoclase predominate, the quartz being subordi- nate to the felspar. The rock at the surface is decomposed. It is cut by a diorite dyke that can be distinguished on the western front from a distance as a black wall running up the entire height of the mount. Smaller portions of graphic and epidote granite are included within the mass.
The hill bears porcupine grass, pine and fig tree, and a light-coloured lichen covers the massive exposures of the granite.
EO ————————
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Low outcrops of gneiss trending in a north-easterly direc- tion he not far to the north of Mount Caroline.
Mount Crombre.—Still further south, and about twenty miles from the above, another conspicuous outcrop of granitic rock, bearing the name of Mount Crombie, is situated. The northern outskirts only of this exposure were visited. They consist of gneiss, whose dark planes of biotite strike roughly east and west. The rock exfoliates concentrically at the sur- face into large shells, which subsequently break up regularly into cubical blocks in well-defined rows, corresponding to a latent system of planes of weakness brought into prominence by weathering. A diorite dyke intrudes the gneiss in direc- tion’ W., 42° N.
Mount Kintore.—Mount Kintore rises from beneath the desert south of the gap that separates the Mann from the Musgrave Ranges. It is built up principally of metamorphic beds intruded by diorite dykes. The beds, comprising gneisses and quartzite, have been thrown into a series of simple folds, which is well recognisable on the northern face of the mount. Gross shattering and crumbling of the rock have accompanied the folding. The strike of the beds varies slightly, about south-east, and it is made prominent by the weathering of the rock into ridges conforming in direction with that of anti- clinal axes.
At the western end of the outcrop the gneiss is replaced by a development of graphic granite; and diorite intrusions traverse the hill in several localities.
Echo Hill.—Echo Hill lies south of the eastern extremi- ties of the Musgrave Ranges. It is one of many minor out- crops of granitic rock occurring in this neighbourhood, and is composed of gneiss neatly “lined” with biotite. Is is cut by veins of coarse pegmatite, with large felspathic constituents, while local developments of epidote are frequent. The rock is jointed in planes striking 8. 40° W., and dipping 40° N.W. The height of the hill is 2,270 feet above sea level (by aneroid determination).
THE Mann RanGEs.
General Remarks.—The Mann Ranges, discovered and named by Gosse in 1873, lie to the west of the Musgrave, and are separated from them by a desert tract of sandhills bear- ing Triodia and Casuarina. They extend as a more or less compact chain in a westerly direction, with a slight trend to the north, across the border of South Australia and the Northern Territory, a distance of some eighty miles. Isolated hillocks can be traced to beyond the border line of Western Australia, culminating to the westward in a more pronounced development, known as the Mount Gosse group of hills. The
E
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trend of the Mann Ranges, if produced in an easterly direc- tion across the intervening tract of sandhills, is in the same straight line as the axis of the Musgrave Ranges.
Both ranges consist of igneous intrusions* and altered sedimentary and igneous rocks. The western portion of the Mann Ranges, of no great width at this end, consists almost wholly of igneous exposures. In the centre the core of igneous intrusion is flanked on either side, namely, its north- ern and southern boundaries, by complexes of gneiss, schist, and gneissic quartzite; whereas on the eastern limits of the range, by far the widest portion, the main intrusion lies hid- den beneath the metamorphic series, into which it was in- jected, to appear once more at the surface to the eastward, in the Musgrave Ranges.
A ground plan of the metamorphic exposures of the Mann Ranges gives roughly a U-shaped form, the flanks that skirt the middle of the ranges forming the straight arms of the U, the curved base of the letter being represented by the thicker mass of crystalline schists at the eastern end.
As a rule, the trend of the ranges coincides with the strike of the rock, except in a few instances, where irregu- larity of stress produced by igneous intrusion has interfered, and where a local bulging out of the mass, no doubt the result of an igneous offshoot, has produced a spur, the axis of which does not conform with the general direction of the range.
Though mineralogically not as rich as the Musgrave Ranges, the Mann Ranges are geologically of particular interest, as they exhibit many examples of rock movements and fracture that accompanied igneous intrusion. +
Igneous Rocks.—An intrusion of granite has been by far the greatest, it continuing uninterruptedly as the backbone of the whole range, to disappear under superincumbent gneisses on the east, and occurring as isolated outliers for a considerable distance to the west. The character of the rock varies, passing from a true granite (in portions porphyritic), tc various metapyrigen gneisses. + ,
—_—_——
* Compare J. Forrest, Explorations in Australia, III., page 243 :—‘‘The Mann Ranges are composed of reddish granite.’’ Also J. Carruthers :—‘‘The Mann Ranges are covered with pines, blood- wood, a few scattered gums, dense spinifex, and scattered patches of coarse grass, the formation being red and grey granite,’’— (Adelaide Observer, January 16, 1892. page 9.) pat
t+ Compare the statement:—“. . . hills and mountains of the Mann Ranges, some few of the Musgrave chain, and all west of the Mann Ranges have been shivered into fragments by vol- canic force, . . .”—E. Giles, Geogr. Travels in Centr. Austr., 1872-1873, Part ii., page 108.
{| The term as employed by Dr. J. W. Gregory.
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The plane of contact with the primary gneisses is mostly imperceptible. A contact zone is not infrequently found gradually merging into granite on the one side, and granitic gneiss on the other. In other cases the contact has been so fractured and dislocated for a considerable distance that the junction cannot be traced.
Large “floating” masses of bedrock were noted at several localities, as, for instance, north-west of Mount Whinham and south of Mount Edwin.
The granite in general occurs as bare, rounded, dome- shaped masses,* several chains’ length of rock often appearing without the least fracture in the mass, though subsequent weathering produces large exfoliating shells, which detach themselves from the body of rock (concentric weathering). This feature is more usually presented by the porphyritic varieties, while a more typical granitic aspect is brought about by the natural systematic jointing of the fine-grained, uniformly crystalline rock. Frequently the mass shows nei- ther of these physical features, but is grossly shattered throughout by the intense stress produced during the process of solidification of the crystallizing rock magma. Such in- stances were found south of Mount Cockburn, and on a splendid scale south-east of Hector’s Pass, where the planes of fracture have assumed regular, contorted, and curved out- lines, as though produced during the last stages of solidifica- tion of the magma, the more rapidly contracting envelope of the rock having caused the enclosed mass to part along cer- tain curves of stress by virtue of the extreme pressure from without.
Diorite dykes are very numerous, forming a fairly regu- lar system, usually, though not invariably, trending east and west. The best noted example of excessive intrusion by this rock was observed in the hills east of Mount Whinham, on the eastern extremity of the ranges. At this locality no less than fourteen diorite dykes can be counted traversing the gneissic hills in a distance of less than a quarter-mile, and can be clearly seen continued through a similar gneissic exposure a mile or two further west.
Metamorphic Rocks.—As stated above, crystalline schists
and gneisses appear more extensively developed at the eastern end of the chain. Near the north-western limit of the main
“ Giles (op. cit.) continues his statement :—‘‘. . . most of the higher points of all these heights are composed of frowning masses of black-looking or intensely red ironstone or granite. eoat- ed with iron. Triodia grows as far up the sides as it is possible to obtain any soil, but even this plant cannot exist upon solid rock. therefore all the summits of these hills are bare,”
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range, the metamorphosed rock, close to the intrusive, occurs as a fine-grained, compact quartzite, passing further from the contact into a garnetiferous gneiss, with large lenticular crystals of felspar (a variety of adularia, or moonstone), hav- ing a satin-like lustre, and which, even to the naked eye, can be seen to be locally surrounded by a layer of finely crushed material derived from the grinding down of the felspar itself (Morter structure).
Fig. 3.—AvcEen Gneiss, Mount Cocksurn, Mann Ranggs.
In the former instance the altered rock was no doubt originally a somewhat massive, siliceous sandstone; in the latter a finely laminated rock has probably been altered by minor injection of igneous matter between the planes of lami- nation (injection gneiss).
South of Mount Cockburn, however, garnet-schist* and fissile gneiss occur at the zone of contact, while gneissic quartzites overlie the gneiss. It is in this locality that a natural section affords opportunity of studying the relative positions of these altered rocks. (Section on Plate xix.) A granitic intrusion appears in the form of a central axial-core,
“ W. C. Gosse writes that Mount Charles is ‘‘composed of grey granite and slate.’? Report and Diary of Central and Western ‘xploring Expedition, 1873. Parliamentary Paper No. 48, House Assembly, 1874, page 12. No slate was observed in this neigh- bourhood, and it may be that Gosse mistook the schist or fissile gneiss for the same. |
69
trending west, which has thrown the overlying beds into a series of simple folds: an anticlinal directly conforms with the surface of the eruptive, and consists of blue garnetiferous schist and gneiss, with “eyes” of felspar, large crystals of hornblende and fractured garnets. South of this spot the overlying beds of gneissic quartzite can be traced, occurring as two perfect sigmoidal folds, the second synclinal, with a very sharp angle, thence passing to a shallow monocline that is finally lost in the zone of crushing at the contact with a second intrusive mass. The extreme southern exposures of the range occur as outlying masses of gneissic rock, the strike of which agrees with that of the country, and the dip is southerly.
At the foot of Mount Cockburn, a low outlier of the same exposures consists of quartzitic gneiss, the foliation being im- perfectly developed, and large, lenticular “augen” of felspar not infrequent. The hill shows perfect parallel planes of jointing in direction N., 15° W., dipping 75° westerly. These planes are made the more conspicuous by the resulting fissures having become filled with detritus, in which a thick growth of grass and other vegetation, standing out as dark, prominent lines from the light-coloured gneiss behind, has flourished.
To the north the augen gneiss merges on the one hand into a gneiss with linear foliation, and on the other into a crushed rock, with large, false “pebbles” of quartz, produced from the original rock, surrounded by well-marked, concen- tric “lines of flow” of crushed material. Shearing and com- pressive stresses have certainly contributed largely to the for- mation of the latter, and like forces have produced the augen gneiss, while the ultimate result of rock-crushing and shearing is the finely “lined” variety of gneiss.
Striking evidence of the extreme conditions of stress that existed during the mountain-building processes is afforded at the north-eastern end of the Mann Ranges in the form of a series of step-faults on a fairly large scale. The country here consists of compact gneiss, with large, bluish orthoclase and folia of biotite, intruded by diorite dykes. Ten distinct, almost vertical, scarp-faces of gneiss, rising one above the other, can be seen, each surmounted by the severed portions of one and the same diorite dyke. The igneous rock, four feet in thickness, forms the floor of each step, the vertical dis- tances between the successive steps averaging twelve feet, and each fractured mass of the diorite dyke dipping about 10° 8. The several fault planes hade 10° in a direction N. LO
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DIORITE
DIORITE \
DIORITE
DIoRitTe
Fig. 4.—STEP-FAULTED GNEISS AND Ditor1tTE DyKr, NORTH-EAST Mann Ranacgss.
_ An interesting phenomenon was encountered in this series of gneisses some dozen miles north-west of the western extremity of the main range, where low outcrops skirt the eastern limit of a large depression or “‘salt pan,” the saline deposits of which rest directly upon a bed of similar gneissic rock. These outcrops have weathered by a process of @olzan erosion into mushroom-shaped masses (Pilzfelsen), with smooth central columns, narrow at the base, and gradually widening upwards to support a flat, tabular mass at the top. The stalk is abraded by deflation, the wind hurling the coarse grains of sand, which do not rise to beyond a few feet above the level of the ground, incessantly against the base of the column. (Plate xiii., fig. 2.)
Streich has reported* mushroom-like forms of sand to occur in the wind-drifted sands of the Great Victoria Desert. He states that the sand is generally loose, though somewhat consolidated by means of a clay cement, but only on the surface. When the uppermost crust has been broken through, the wind gradually blows away the underlying loose sand, leaving the upper layer unsupported around the
* Scient. Res. Elder Expl. Exped., 1891-2, Geology. Trans. Roy Soc. S.A., vol. xvi., page 88
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border. The phenomenon is really resistance to transpor- tation of the consolidated crust by wind rather than abrasion or erosion of the underlying loose sand by eolian agency.
A further factor that plays an important part in the weathering of rocks in the desert was noted in the outcrops of garnetiferous gneiss immediately west of the shores of Lake Wilson. This form of weathering, the Seele der Ver- witterung of Schweinfurth, consists of the flaking off of the rock as a result of crystallisation of salt within minute fis- sures in the mass. Portions of the outcrops, that have been previously locally hardened by cementation (concretionary), have resisted this weathering to some extent, and consequently those portions project from the surface of the decomposing gneiss as irregular, partly serrated, ridges, the direction of which is usually consistent with that of an original constant geological feature of the rock.
Veins, etc.—Comparatively few true fissure veins or lodes were noticed in the Mann Ranges. At the salt pan just mentioned an exposure of a “quartz reef” occurs in com- bination with a coarse pegmatite /7.e., secondary quartz, in the intrusive). The quartz of the “reef” is very coarsely crystalline, the faces of the prisms exhibiting oscillatory com- bination to a marked degree. The felspar of the pegmatite occurs as large pink idiomorphic crystals of orthoclase. The lode is non-metalliferous.
A common method of formation of so-called “quartz blows” in the ranges is nothing more than metamorphism by igneous intrusion into the bedrock, the ultimate product
consisting of a highly altered quartz schist. The best example of this phenomenon was met with south-east of Mount Edwin. The quartzose outcrop there consists of
three parallel ridges of metamorphic quartz schist and granular quartz, the planes of schistosity of the former being visible either as thin layers of secondary mica or the direct products of decomposition of the same. The outcrop trends W. 40° S., and is jointed in directions: (a) N.E., dipping 70° S.E., the rock being finely laminated in this direction, and the planes of lamination a fraction of an inch in thickness; (b) N.W., in well-defined, parallel planes, few inches apart; (c) W. 10° N., and N. 20° W., in less perfect partings. This quartzitic exposure is, beyond doubt, a true product of contact metamorphism, and the difference between its strike and that of the country is explained by parallel outcrops of garnetiferous diorite dykes between the separate ridges of the formation; for these have been the cause of the metamorphism of the original schistose beds lying directly in contact with them.
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Owl and Bat Guano.—In the Mann, Musgrave, and Ayers Ranges. caves were found containing a considerable floor deposit of so-called guano, the droppings of owls and bats. These caverns have been produced in the granitic rock masses by the denudation and subsequent removal of included softer portions or by the more rapid weathering of the material along planes of parting in the rock. In the former case they were usually observed opening out on to
the bare, more or less vertical, joint faces. Owls (princi- pally Strzx delicatula) appear to be frequent inhabitants of such caves at the present time. Similar deposits were dis-
covered in the Fraser Range by the Elder Expedition.*
The “guano” consists of a faintly yellowish to dirty white, compact to flaky, or lamellar mass, with a peculiar, penetrating odour resembling that characteristic of the ex- crement of flesh-eating birds. The bottom and oldest layers of the deposit have assumed, not invariably, a more or less elastic character when in mass, making it somewhat difficult to detach in small pieces with a hammer. It breaks away as distinct layers or slabs.
In April, 1902, Mr. H. Y. L. Brown reported’ ton cave deposits occurring in quartzite near Yunta. The “guano” from this locality is almost identical with that from the ranges of Central Australia. _ I have had opportunity of comparing hand specimens collected by Mr. Brown with those I gathered in the Mann and Ayers Ranges. An analysis of guano from the Yunta caves made by Mr. Goyder proved the presence of phosphoric acid and nitrogen in diffe- rent samples in the following proportions: —Phosphoric acid (P,U,): (a) 55; (b) 6°00; (c) 2°57 per cent.; and nitrogen: (a) 1°68; (b) 23°44; (c) 6 per cent.t It is evident from the above estimations that some of our cave deposits are equal to high-class manures, though it may hardly be expected that. they will ever become of commercial value. n account of their limited extent, to say nothing of the troublesome journey to the above ranges.
Analyses of cave deposits have also been published from Victoria and New South Wales.§
* V. Streich: Trans.. Roy. Soc. S.A., vol. xvi., page 99.
+ Report of Government Geologist to Minister of Mines, April, 1902.
t See Macivor, On Australian Bat Guano, ete,, Chem. News, May 13, 1887, page 3. .
§ Notes and Analyses of Some N 8.W. Phosph. Minerals and Phosph. Deposits. by J. C. H. Mingaye, Aus. Asso, Adv. Se., vol, vii., 1893, page 382. ;
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Mount Gossez, W.A.
Mount Gosse is situated in Western Australia, about
two miles from the boundary of that State and South Aus- tralia, and ten miles north of the projected border line between the Northern Territory and South Australia. It is composed of an intrusion of granite within schistose to granitic gneiss, the foliation of which strikes west, slightly north. The rock shows cubical jointing, and the gnelssic rocks are overlaid by a compact blue quartzite* possessing a perfect conchoidal fracture, the whole formation being tra- versed by the never- failing diorite. _ A prominent hill, situated seven miles east of north of Mount Gosse, and almost on the border line, stands 2,250 feet above sea level, and 325 feet above the desert, which bears Xanthorrhea and Triodia. It has been determined by an intrusion of granite, with porphyritic blue felspars, the trend of the intrusion being slightly north of west.
The injection lies within a linearly foliated gneiss, show- ing closely set veinlets of quartz. In portions the gneiss is schistose, or slightly fissile, and passes to a fine-grained, felsitoid quartzite. Minor veins of graphic granite, with a white (decomposed) felspar matrix, and epidote, are also met with.
ToMKINSON RANGES.
General Remarks.—These ranges occupy the north-west- ern corner of the State of South Australia proper, and ex- tend westward to beyond the border into Western Australia (Mount Hinckley). They were named by Gosse in 1873. Generally speaking, their dominant features are similar to those of the Musgrave and Mann Ranges, namely, igneous intrusions within crystalline gneisses. In the case of the Tomkinson Ranges, however, the intrusive rock consists largely of gabbro, accompanied by diorite dykes. Moreover, the ranges are not as persistent and compact as those already described.
The higher intrusive bosses bear scanty vegetation, as porcupine grass,{ mallee, and pine, while the lower spurs of gneiss are covered with mulga and kangaroo grass. The intervening gullies and flats were thickly clothed with grass and herbs.
eres Phe emenigan at Midarie Gosse. Js a ‘iinet with: ‘Ere! quent diorite veins and dykes, W. R. Murray, Ex- tracts from Journals of Explor ations, by R. T. Maurice (by Autho- rity: 1904), page 17,
t+ See also E. Giles, Geogr. Travels in Centr. Austr., 1872- 1874, II., page 103; and J. Carruthers :—‘‘These hills are covered with spinifex, : —Report to Surveyor-General (Adelaide Observer, January 16, 1892).
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The Mount Davis chain includes, among others, a large intrusion of granular olivine-gabbro, * varying in colour from dirty green, through various shades of green, to faint blue. In the last case the predominance of plagioclase fel- spar and the presence of only a small amount of olivine have produced the bluish tint. The intrusion trends east and west aS a massive, rugged chain, flanked by less conspicuous diorite dykes.
The latter, though individually smaller, are very nume- rous. Their direction of intrusion possesses no regularity, often cutting one another at various angles. Upon one hill, about three miles south-east of Mount Davis, two conspicuous diorite dykes can be traced up the hill slope. These dykes gradually converge towards the summit of the hill, where they ultimately cross one another at an angle of about 30°, each continuing its cwn course after the point of crossing. The direction of intrusion of the diorite appears more con- stant (east and west) on the northern side of ihe ranges than is the case of the more numerous examples on the south.
Very often smaller dykes can be traced in a direction nearly at right angles to the larger, from which latter they have been injected into minor fissures of the rock. The trend of these smaller dykes, in several cases, was noticed to correspond with that of the pianes of foliation of the in- truded gneiss, and their outcrops can be traced down to the adjacent sandy flats, from which they stand out, by their superior weathering, as marked, low, parallel walls.+ As a general rule the diorite rock of the Tomkinson Ranges is of one type only: a finely crystalline, black-looking (horn- blendic) variety.
A few miles south of Mount Davis a slight exposure of graphic granite occurs. The quartz that produces the hiero- glyphic markings on the surface of the rock is colourless and embedded in a red orthoclase felspar matrix. The whole rock is traversed by veinlets of crystalline epidote.
* J. Carruthers, op. cit.: ‘‘The Tomkinson Ranges .. . are composed of grey and red granite, with large outcrops or dykes of basalt.” No basalt was found in the neighbourhood of the Tomkinson Ranges, and it is possible that the gabbro was mis- taken for basalt by Carruthers. W. C. Gosse, Report and Diary of Central and Western Exploring Expedition, 1873, Parliamen- tary Paper No. 48, House Assembly (1874), page 13, writes :— “Mount Davis must be at least 1,500 ft. high. This portion of the range is composed chiefly of grey granite.’ W. R. Murray,
Extracts Journals of Explorations by R, T. Maurice (by autho- rity: 1904, page 17).
+ Which Mr. Streich compares with the ‘‘ruined walls of houses.’’ Scient. Res. Elder Expl. Exp., Trans. Roy. Soc., S.A., vol. xvi., page 93.
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Metamorphic Rocks.—The gneisses occur as broken spurs and ridges, extending far outward into the sandy plains. On the north their character is granitoid and foliated, the planes of foliation striking north-easterly. The rock is character- ised by bands of quartz and the presence of secondary mine- rals in more or less distinct layers.
North of Mount Davis outcrops of hypersthene-bearing granulite, which trend slightly east of north, present splen- did examples of spherulitic weathering (Augelige A bsonder- ung). This rock is compact and granular, with little or no evidence of foliation on freshly fractured surfaces, though it is apparent on weathered faces. The rock has a peculiar olive-green waxy appearance.*
The most westerly exposure of the Gosse’s Pile Spurf consists of gneiss, which is normal, though quartzitic, the quartz occurring in the form of elongated lenticles, and the mica as small flakes in regular layers of no great thickness. The rock is thickly studded with red garnets (Almandine). This class of gneiss predominates in the Tomkinson Ranges, it being also met with south of the main range.
Veins, ete.—Non-metalliferous quartz veins of a bluish tint and a shattered glassy character are fairly plentiful. They are usually seen in direct association with diorite dykes.
The Murru Yilyah Outerop.—This outcrop, which was stated to be auriferous, skirts the northern foot of the Mount Davis chain for some miles in a westerly direction (W. 20° N.), with a prominent escarpment facing the north. The de- posit consists of a fresh-looking, highly-siliceous rock, vary- ing from an impure siliceous ironstone through chalcedonic and semi-opaline varieties of quartz, the chalcedony often occurring, encrusting, drusy or slightly stalactitic, or per- vading the rock as irregular planes of infiltration. The silica has been tinted by mineral salts in solution, the colour rang- ing from a rich brick-red through pale yellow to a bright green (chromium). Small, irregular cavities exist in the rock, which are either coated with a drusy form of quartz or filled with haematite, compact to cellular. The rock breaks with a conchoidal to sub-conchoidal fracture, and small frag- ments, the result of weathering, cover the adjacent slopes and
* Mr. G. W. Card, of the Geological Survey of New South Wales, who examined a section of this rock for me, writes that the hypersthene is not very abundant, and is of a deep colour. Apatite is present in noticeable amount. The bulk of the rock consists of granular quartz and felspar. Granulitisation and_re- crystallisation are not complete in the case of the felspar, residual portions of which may still be seen.
% ee a ‘“‘Gosse’s Pile Hill is of grey granite, with diorite, Se . R. Murray. op. cit., page 17.
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flats. A pseudo-brecciated appearance within the rock is produced by simultaneous precipitations of compounds of iron and chromium and chalcedony. Surface cappings of travertine and small deposits of magnesite rest upon the out- crop in places, and more frequently upon the diorite dykes in proximity to it. The deposit is of no great thickness, and can be seen on the west directly overlying diorite. Its origin is doubtful, as it can hardly be referred to the “desert sand- stone,” though in some respects it 1s not dissimilar to it. The formation has been proved to be non-auriferous.
EVERARD RANGES.
General Remarks.—The Everard Ranges he to the south of the Tomkinson, and south-west of the Musgrave Ranges. They are the most southerly of the series of elevations in Central Australia, the other members of which have already been described. They were discovered in 1873 by Ernest Giles, and subsequently (1891) visited by the Elder Expedi- tion.. Mr. V. Streich, the geologist to that expedition, points out* that the Everard and Birksgate Ranges consist almost entirely of eruptive granite, although representatives of a schistose series overlying the granite were observed, usually as outliers of the main range. Mr. Carruthers also pointed out that they ‘‘are chiefly composed of red granite.’+ Only the eastern limits of the range were visited by the North- West Expedition, although the main granitic chain, with Mount Illbilhe as a prominent feature, was sighted in the distance, and therefore the following notes relate to that por- tion of the range only.
Igneous FRocks.—True granitic intrusions, often with large porphyritic felspars, have penetrated granitic gneiss. The granite at the borders of the intrusions has assumed a gneissic character, the apparent planes of foliation having a waved and plicated outline. These planes have, beyond doubt, been produced by movement of the rock magma after partial crystallisation of the constituent minerals. Veins of epidote and epidote granite, in which epidote replaces mica, are general, while interrupted veins of coarse acid secretions are not infrequent.
The intrusion of the granite has taken place in a direc- tion a few degrees south of west, and the weathering of the softer portions of the rock has left huge, bare massifs, upon
* Scient. Res. Elder Expl. Exped., Trans. Roy. Soc., S.A., vol. xvi., page 83.
; ov Rep. to Surveyor-General (Adelaide Observer, January 16, 1892).
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the surface of which lie boulder-shaped tors that often rest in perilous positions.
Diorite and pegmatite dykes occur in fair number, the former more frequently than the latter.
Metamorphic Rocks.—The gneiss occurring in this locality is, without exception, granitic and largely “meta- pyrigen.” The best exposures that came under notice are those occurring south-east of Artootinna soakage well. At this spot the planes of foliation, greatly contorted and folded, strike easterly, and the rock is vertically jointed in direction north and south. The foliation is made conspicuous by planes of dark-coloured biotite, the mica in the original in- trusive mass being in parts poorly developed or absent.
Veins, ete.—Veins of barren quartz within the bedrock are not wanting. To the east of the ranges, further, small pegmatitic veins exist within the gneiss, containing irregular secretions of magnetite.
AYERS RANGES.
General Remarks.—The group of hills, situated for the most part in the southern limits of the Northern Territory and partly in South Australia proper, and generally known as Ayers Ranges, is hardly deserving of such a geographical term. In appearance the hills are similar, though smaller and more disconnected than the previously mentioned groups of elevation. Mr. Ernest Giles, describing these ‘‘ranges,” which he discovered in 1872, from the summit of Mount Sir Henry, stated* that “the mount and all others connected with it rose simply lke islands out of a vast ocean of scrub,” and that the mount “consisted of enormous blocks and boul- ders of red stone, so riven and fissured that no water could lodge for an instant upon it.”
The hills are of fair altitude; yet they appear compara- tively low. This is because the red sands from which they rise cover their flanks to a considerable height. The highest point, Mount Cavenagh,; stands 2,200 feet above sea level, but only 300 feet above the adjoining sands. They may be divided into three groups: firstly, that comprising Mounts Cavenagh, Barrow, and Reynolds, all of which are portions of the same outcrop and in proximity to one another ; second- ly, Mount Sir Henry, situated about three miles south of the former ; and lastly, a prominent southern ridge that extends into South Australia proper. All these prominences have been determined by igneous intrusions, the first two sets con- sisting of granite, the last of an extensive belt of diorite dykes.
* Geogr. Travels in Centr. Austr., 1872-1874, I., page 78.
+ Mount Cavenagh of Giles was re-named Mount Burton by Carruthers’ party.
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Lying between these masses, disconnected, rounded hills of metamorphic rock appear, rising, as In previous instances, from a vast expanse of sand.
Igneous Rocks.--The granite is somewhat coarsely crys- talline, normal to slightly porphyritic, the felspar often oc- curring as porphyritic individuals. Magnetic ores of iron are plentifully developed. The rock is superficially rotten. The mass shows typical granitic features, with a regular, ver- tical system of jointing, which sometimes, by weathering, have formed large caves, notably north-west of Mount Cave- nagh. The intrusion appears to have occurred in a direction north of west, and the Mount Cavenagh outcrop is divided by a series of parallel gullies running in a northerly direc- tion. Outcrops of identical rock were found intermediate in position between Mount Sir Henry and Mount Carnarvon, thus geologically connecting the Musgrave and Ayers Ranges. About fifteen miles south of Mount Cavanagh a different type of granite is found adjacent to a belt of dioritic intru- sion. It is a highly felspathic graphic granite, the felspar being a light red orthoclase, and in parts is pegmatitic. Fur- ther east it has suffered considerable metamorphism, and _ is veined by saussuritic rock and a coarsely crystalline, fels- pathic, acid modification.
Diorite intrusions are exceedingly plentiful. The south- ern extremity of the ranges is a pronounced ridge, rising atout 200 feet above the plain, about a mile wide, and extending for several miles east and west. It 1s composed almost en- tirely of diorite intrusions, with the exception of a few “‘float- ing’ masses of highly altered rock in the same. The dykes trend within a degree or two of due west, and are either re2u- larly jointed into quadrangular blocks or weather into round- ed masses resembling granitic tors. Between this prominent ridge and Mount Sir Henry a marked series of parallel diorite dykes, usually of no great thickness, continues for nearly the whole distance, a dyke being met with at every few chains. Their direction is east and west, with very few exceptions. A few low exposures of the bedrock were met with, consist- ing of various modifications of altered granite.
Metamorphic Rocks.—The gneiss has its greatest develop- ment in the east of the ranges, occurring as more or less iso- lated bare hillocks. It is linearly foliated, the planes of foli- ation striking N. 10° E., and dipping W. at Kurrekapinnya soakage. This fact seems extraordinary, as in all other cases noted the foliation of the gneiss coincided in direction with the trend of the intrusion, and this evidence, in conjunction with other physical features, has suggested a change in the direction of intrusion of the granite. The rock is jointed in
19
well-defined planes, striking W. 25° N., with a northerly dip, and, less conspicuously, in planes striking N. 3° E., with a dip of 75° W. Secondary minerals line the walls of these joints, along which, moreover, slight faults and hitches have occurred.
THE INDULKANA OUTCROP.
About twelve miles east of Indulkana Spr‘ug, adjacent to Chambers’s old wagon track, a small exposure of bedrock exists, and, whilst not many square miles in extent, indica- tions are not wanting that the rock may be found at no great depth over a much wider area. The exposure is 1,300 feet above sea level, and is surrounded on all sides by a capping of “desert sandstone” barely exceeding 30 feet in thickness.
Igneous Rocks.—The intrusive rocks are of the acid and intermediate families. Diorite dykes predominate, though it is often difficult to determine the exact planes of contact with the intruded schists on account of the severe shattering of the rock. At least four major diorite intrusions have occur- red in direction east and west, with slight variations, due possibly to subsequent earth movement. The largest mea- sures one hundred yards in breadth. In places where the con- tact with the schist is visible the latter rock appears baked and highly schistose, with upturned planes of schistosity. The diorite is for the most part fine-textured, quartzless, and micaceous ; on the surface the rock is usually “honeycombed” by unequal weathering of the constituent minerals, the lbe- rated iron oxides coating the surface with a “rust.”
Intrusions of graphic granite, pegmatite, and greisen have occurred previous to that of the diorite. This is evident from the fact that the diorite dykes are often found cutting the pegmatite, the latter having thereby frequently suffered lateral displacement. The mineralogical character of these acid rocks varies considerably. Their common feature is coarse crystallisation of the constituents. Im some dykes quartz predominates, in others it is subordinate to felspar, while mica occurs as irregular aggregates in the greisen and occasionally as an accessory in the pegmatite—in the latter case usually in a state of partial decomposition. On the western limits of the exposure igneous intrusion is marked by dykes of graphic granite and schorlaceous greisen, the lat- ter including large, perfect crystals of black tourmaline and a light-coloured microline., The general direction of intrusion is east and west, although dykes may be found running at right angles to this. True granite is feebly represented by a coarsely crystalline rock, with pink crystals of orthoclase, rather subcrdinate quartz of a bluish sub-opaline character and a greenish biotite.
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Metamorphic Rocks.—In traversing the outcrop from south to north a gradual alteration in the structure of the bedrock will be noticed, the rock grading from a quartz mica schist on the south, through a highly micaceous black biotite schist, to a finely foliated quartzitic gneiss, to a typical augen gneiss on the north. The strike of the beds varies (in zones of extreme pressure considerably), though the general direc- tion appears slightly south of west. The dip is doubtful, possibly northerly. The augen gneiss, compact and granitic, contains lenticular veinlets of quartz, which are often con- siderably distended as a result of lateral pressure during a state of semi-plasticity, and in addition are frequently found turned upon themselves or complex-folded. The schist can be distinguished from the gneiss in the field even at a dis- tance by contrasting its serrated lines of outcrop with the rounded, massive, boulder-like outcrops of the gneiss. On the north-east the rock consists of a rotten biotite schist, in which planes of mica have become so aggregated that the rock appears to be almost entirely built up of the pure mineral biotite. Even in hand specimens the curved and crinkled lamelle of the mica indicate how great a stress the beds have been subjected to. The planes of schistosity of the rock strike from 10° to 20° south of east, and dip N. 32°. The beds are further jointed in directions E. 10° S8., with a dip of 60° S., N. and S., with a dip of 85° W., and irregularly by a poor vertical plane. To the south this rock becomes less per- sistent, and has yielded more to weathering. A small de- velopment of chlorite schist occurs in contact with the augen gneiss, and a local production of hornblende epidote schist has taken place at the contact with certain diorite dykes. Skirting the north-western limits of the outcrop a finely crys- talline gneiss seems to point to a zone of crushing of an igneous rock. (See Appendix. Pages 94-5.) Outcrops of quartz schist, mica sckist, and gneiss extend more or less con- tinuously westwards to Indulkana soakage well, at which spot the gneiss contains coarse vein-segregations of felspar with a development of tourmaline and titaniferous iron ore. Repeated searching for tin ore proved fruitless.
Some miles south of the main outcrop low surface expo- sures of ferruginous clay slates and mud stones appear, the sharp, serrated edges of the same standing out conspicuously. In some parts the rock comes near to a phyllite, and is tra- versed by very many small quartz veins.
Veins, etc.—The so-called “quartz reefs” of the locality are of two kinds, namely, those forming portions of a true igneous (pegmatitic) dyke, and those formed subsequently by deposition freza solution in fissures of the rock. The latter have a remarkably fresh, compact, crystalline appearance,
81
and in no case do they extend downward to any depth, but pinch out in less than a dozen feet; they are the fillings of wedge-shaped fissures within the diorite dykes. A _ typical instance of a “reef” occurs one mile east of Krupp Hill. It measures four feet in width at the surface, but its walls rapidly converge to a point in depth. The fissure walls strike E. 8° S8., the northern wall dipping 60° S., the south- ern 80° S. The quartz is either milky or glassy. The for- mation may be termed a ‘“‘dead lode,’’* although pyrites is disseminated through the vein, and in_ one _ instance deaewrace j.Ol) grey) copper ore was discovered. The pyrites crystals that impregnate the mass are decomposed near the surface, leaving small cavities containing sulphur and a little limonite, the remaining pro- ducts of decomposition haviny stained the numerous cracks and crevices in the quartz. Shght quantities of secondary minerals (chlorite) occur locally, and the walls of small cavi- ties are coated with drusy quartz. ;
Few miles west of Indulkana soakage a lode of siliceous ironstonet stands out conspicuously from a fissure in the crystalline schist. It is possible that this lode overlies a dio- rite dyke.
CAMBRIAN.
No representatives of the Cambrian system were dis- covered in the vicinity of the north-western ranges, none of the contact rocks having disclosed any trace of organic re- mains in any shape or form. However, limestones that must without hesitation be correlated with the Cambrian strata of the Flinders Range occur at the head of Lake Torrens. The outcrop occupies but a small area at the surface, being about three miles in length, in direction east and west, by two miles north and south. The beds are massive, though they extend to no great vertical height above the general level of the country; they stand as large, separated blocks resting upon a more compact body of rock below. The beds seem to strike westerly, although considerable variation (up to N. 25° W., and more) were observed. On the southern limits of the exposure they have the form of a slight syncline, the dips of the strata on either side of the axis of Poin s bem tows i! (120% Witands 2° respectively). They are jointed vertically in two directions at right angles to one another. The rock mass, as a
* One sample of this rock, that was subsequently assayed, re- turned a mere trace of gold (accidental ?). t Mr. H. Y. L. Brown has noted a ‘‘lode outcrop of ferrugi-
nous quartzite and iron oxide’’ to occur in this locality, and is probably the same as that referred to.
F
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whole, shows no signs of bedding, but the impurer portions (siliceous) exnipit faintly planes of deposition and current bedding that are rendered more apparent on partial denuda- tion of the rock. .The character of the rock varies from a bluish, sub-crystalline limestone to a granular marble, to be in parts replaced (in the upper layers) by coloured siliceous and dolomitic limestones. The crystalline limestone con- tains accessory minerals, as small, perfect crystals of fluorite and aggregates of ankerite, while carbonates of copper occur as locally concentrated fissure fillings and pockets of incon- siderable magnitude or quality. Chert nodules that have possibly been derived from solution of contained radiolarian tests, or enclose the spicules of Cambrian sponges,* weather from the surface of the limestone, by virtue of their superior hardness. They are flattish-ovoid in shape, and are bounded by regularly curved, smooth surfaces.
ORDOVICIAN.
Exposures of beds of the Ordovician period were met with in districts widely separated from one another, namely, at Indulkana, Mount Conner, and the Mount Kingston out- crop.
Se ee H. Y. L. Brown visited this outcrop in 1889, and reported? similar rocks to extend in a direction southward to Arcoollina Well, and for a long distance west- wards. Mr. V. Streich passed the same outcrops two years later, { and traced the western boundary of the same forma- tion to Townsend Ridge, over one hundred miles beyond the border line of Western Australia.
On approaching the Mount Chandler range from the north, it has the appearance of a tableland, with its surface sloping slightly westward. This is not, strictly speaking, the case, for, on entering the range, it is found to consist of a series of parallel ridges trending from east to west. The whole formation at this locality appears in the form of a shallow, synclinal trough, the axis of which pitches east and west. The strike of the beds is E. 5° §. The rock is composed principally of a
* Since writing this paper Mr. R. Etheridge, jun., of Syd- ney, has kindly examined a section of one of these nodules for me. He writes that, ‘‘the micro-section of the nodule appears to consist of calcite and chalcedony, with perhaps a third undeter- pee mineral. I cannot distinguish any trace of organic strue- ure,
t H. Y. L. Brown: Report on Journey from Warrina to Mus- grave Ranges (by authority: Adelaide, 1889).
t V. Streich: Scien. Res. Elder Expl. Exped., 1891-2, Geo- logy. Trans. Roy. Soc., S.A., vol. xvi., page 80.
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hard, compact, fine-grained quartzite, merging in parts to a more friable sandstone and grit, portions being ferruginous. A prominent parting of the rock coincides with the original planes of bedding, while further two joints, not very persis- tent, occur: one in direction N. 20° E., dipping 65° easterly, and another at right angles to this. Planes of shear are highly polished by shcekensiding, and in parts the rock has been severely fractured. Drift bedding is much in evidence, and makes the determination of strike somewhat difficult at the eastern limit of the outcrop. The rock has a tendency to cavernous weathering, one of the largest caves having been occupied as a store by the Government surveyors.
The quartzite overlies unconformably schists and clay slates, the planes of schistosity and cleavage of which stand at a high angle. The direct junction is for the most part hidden by the “waste” of rock that has accumulated at the foot of the escarpment, but in a small watercourse on the east the direct contact can be observed for a limited distance, the quartzite resting upon decomposed clay slate.
Although the underlying pre-Cambrian beds are exten- sively intruded by diorite, pegmatite, and other dykes, no such intrusion was observed to penetrate the overlying quart- zite.* The same is true with regard to large quartz reefs occurring in the immediate neighbourhcod. From Mount Chandler the quartzite extends eastward as low, disconnected ridges, and was subsequently found at Camp 7 (Krupp Hill) overlying pre-Cambrian schists, but not overlain by desert sandstone, which, hcwever, directly overlies low outcrops of pre-Cambrian rocks in the vicinity. This fact would in-
dicate a fair altitude of the quartzite during late Cretaceous times.
At Ewintinna soakage outcrops of the same formation take a northerly curve, the beds locally striking N. 25° E. The rock at this spot is, similarly, a quartzite, slightly band- ed and sub-fissile, and in parts traversed by numerous wavy veinlets of secondary quartz. The rock is parted by a promi- nent strike-joint, dipping about 75° westerly, and another plane dipping 85° in the direction N. 25° W. A few miles south of this soakage the quartzite was found to have its strike identical with that of the Mount Chandler outcrop.
Mount ConnEer.—This monolith, rising to a height of 2,600 feet above sea level, and about "800 feet above the level
Goneare. “ie ene —_ é the sranite and other dykes and quartz reefs do not oe into these rocks.” H. Y. L. Brown, Report of Geological Examination of Country in
Neighbourhood of Alice Springs (by Authority: Adelaide, 1890),
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of the desert in which it stands, forms one of a remarkable series of three conspicuous landmarks situated north of the Musgrave Ranges; the other two being known as Ayers Rock and Mount Olga. Mount Conner, rising abruptly from the surrounding desert, is a huge, table-topped outlier of a once continuous extensive geological formation. The base of the mount has a circumference of about six miles, while the plat- eau itself is roughly two miles long by three-quarters broad. It is surrounded on all sides by a talus, having an angle of repose of from 30 to 35 degrees ; above the talus an abrupt es- carpment rises to the edge of the plateau, a vertical distance of about 250 to 300 feet. | With the exception of one or two pine trees the escarpment is practically destitute of vegeta- tion.
The rock is a close-grained, compact, siliceous quartzite. The beds show a pronounced horizontal parting, correspond- ing with the original planes of bedding, and the rock is in portions sub-fissile and fractured, the cracks and _ crevices affording shelter for numerous hawks and owls.
The topmost layers of the rock are composed of a glossy, white, hard quartzite, while the lower portions assume a softer, arenaceous character, and are stained red by precipi- tated products of decomposition. In places the quartzite con- tains irregular bands of well-rounded pebbles of altered sedi- mentary rock (banded and black quartzite), producing locally a conglomerate. Peculiar false-bedding-like markings are found, not infrequently surrounding these conglomeritic por- tions, and the quartzite contains segmented ferruginuus segregations, which are not altogether unlike orsanic remains. The strike of the rock varies from west up to 30° north of west, the beds forming a shallow synclinal fold. Portions of the quartzite are shattered into small blocks, fairly regularly bounded by conchoidal surfaces, huge masses being 1n cases thus reduced to fragments, lying loosely together in a state of unstable equilibrium. This phenomenon is a direct result of insolation. (Plate xiv., fig. 2.) Mount Conner 1s surrounded by low, rugged outcrops and ridges of fissile quartzite, “covered with dense mulga”’ and “marked by a low cliff.’* The quartzite is band- ed, and weathers into large flat slabs. The strike varies.
THE Mount Kincston Ovutcrop.—Mount Kingston is situated west of Mount Watt, the portion of a southern Or- dovician outcrop that was examined by Messrs. Tate and
* W. H. Tietkens: Journ. Cent. Austr. Expl. Exped., 1889, page 59,
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Watt on the Horn Expedition. These authors report* that Mount Watt is composed of a hard, dense quartzite, much fissured, and with few ferruginous bands. Fossils were ob- tained in the form of casts in large numbers in the quartzite.
The exposure} examined by us is situated about six miles south-west of Mount Kingston, and appears in the form of three or four well-defined parallel ridges trending north-east- erly. The rock is a compact, fine-grained quartzite, in parts highly ferruginous. In certain zones the rock is fissile, break- ing into fairly large slabs from a fraction of an inch to seve- ral inches in thickness. The strike is E. 36° N., and dip 60° north-westerly. The beds are jointed in directions N.W., dipping 60° N.E., and N. 10° W., dipping easterly at a low angle. A ferruginous coating is found covering slickensided surfaces, and bands of highly ferruginous rock occur within the rock. A concretionary structure and dendritic precipi- tations of iron oxide are common.
The outcrop aopears in the midst of the desert sandstone tablelands, the broken outliers of which surround the quartzite on almost every side. Its physical features are, however, quite distinct from those of the table-top formation, although hand specimens of the two formations may be not altogether dissimilar.
The height of the exposure above sea level, by aneroid determination, is about 1,950 feet, and about 260 feet above the level of the sand.
Mount Outca anp AvERS Rocx.—No doubt exists in my mind that Mount Olga and Ayers Rock are isolated rem- nants of the Ordovician system, the former consisting of a conglomerate, { the latter of a coarse metamorphic grit. These features suggest that Mount Olga was probably situat- ed close to the old Ordovician land surface, Mount Conner being distant, and Ayers Rock in a position intermediate be- tween the two.
The geologists of the Horn Expedition § have alreaciy hinted at the possible Ordovician age of Mount Olga and Ayers Rock, while Mr. Brown, judging from specimens col-
™ Tate and Watt: Rep. Horn Exped. Centr. Austr., General Geology, page 59. _ + Mr. Wells has erected a small! pile of stones on the highest point of this exposure.
t Compare W. C. Gosse, Parliamentary Paper No. 48, House Assembly, 1874, page 11:—‘‘This range is formed of a number of round-topped masses of solid conglomerate rock (known as pud- ding stone), but with stony, spinifex slopes, from 100 to 300 fesi rising to their foot. Each hill is a separate rock.”
§ Tate and Watt: op. citl., page 59.
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lected by Mr. Tietkens, was inclined to consider Mount Conner younger than the other two members. *
DESERT SANDSTONE.
The term Desert Sandstone, which was originally used by Daintree for a highly siliceoas deposit that is often found overlying the fossiliferous Cretaceous of Australia, is, to a cer- tain extent, misleading, as the formation is only to a hmited extent a true sandstone. Mr. H. Y. L. Brown employed the term Super-Cretaceous, and later Professor Tate and Mr. Watt Supra-Cretaceous, for the same formation. Messrs. Jack and Etheridge regard the desert sandstone as Upper Cretaceous.
No conclusive evidence concerning the exact relationship was found, but I observed that the desert sandstone in many places, particularly at Indulkana, unconformably overlies intruded primary schists. This fact, if the formation is to be correlated with the cretaceous, would demand, as Professor Tate suggested, that the desert sandstcne overlaps the latter
Beds