Dynamics of nerve and muscle

Front matter

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Preface

a transitory step towards rigor mortis — a change brought about by something being abstracted from the muscle, not by something imparted to or awakened in it — even a physical rather than a vital phenomenon. Is it possible, I asked myself, that life may show itself, not in causing contraction, but in keeping the muscle relaxed, and that the doctrine of muscular motion may need reforrriing in accordance with this idea ? Nor was I long undecided as to the answer which had to be returned to this question.

Shortly after this time, I published a small volume* with the object of showing that the doctrine of muscular motion did need reforming in accordance with this idea, and about which I may say what Dryden said concerning one of his own plays — “ it was only a confused mass of thoughts tumbling over one another in the dark, when the fancy was yet in its first work, moving the sleeping images of things towards the light, there to be distinguished, and then either chosen or rejected by the judgment.” Nor can I look back with feelings of pride at later efifortsf in the same direction — not even at that, the latest of all, which took the form of lectures delivered at the Royal College of Physicians of London, in 1863, and published soon afterwards.f I did the best I could

* “ Philosophy of Vital Motion.” 8vo. London: Churchill, 1851.

f “Epileptic and other Convulsive Affections of the Nervous System : their Pathology and Treatment (incorporating the Gulstonian Lectures for i860). 3rd edition, post 8vo. London : Churchill, 1861.

$ “Lectures on Epilepsy, Pain, Paralysis, and certain other Disorders of the Nervous System,” delivered at the Royal College of Physicians of London. Post 8vo. London: Churchill, 1864.

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v at the time, but I can easily see now that the best I did was not done well enough to carry conviction to a mind which did not share my own convictions. I can see that I succeeded better with the pathological part of my argument than with the physiological. I can see that the latter part was very faulty for want of work with which my leisure moments have been a good deal occupied during the last two years, and of which the results are incorporated in these pages.

Very soon after my thoughts upon this subject began to take definite form it became apparent to me that the key to the dynamics of nerve and muscle lay hid among the facts belonging to animal electricity. Fascinated by the results to which the investigations of Dr. Du Bois-Reymond had led, my attention was at first solely directed to the aspect of animal electricity which is made known by the galvanometer. At this time the muscle-current and the nerve-current, and their changes when passing from the state of rest into that of action, seemed to be the all-important facts which ought to be noticed. Afterwards I slowly began to apprehend that there was another aspect of animal electricity which is ignored in these investigations. The fact, discovered by Matteucci, that muscular contraction was accompanied by a discharge analogous to that of the torpedo, seemed to point, not to the muscle-current and nerve-current as primary and fundamental conditions of animal electricity, but to a state of charge, and for the evidences of this charge I began to seek, first with this electrometer and then with that, first

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PREFACE .

with this condenser and then with that, and not altogether fruitlessly even at first. I made out something by an electrometer of my own contriving. I thought I had . done more by means of the Potentiometer of Mr. Latimer Clark, but the end proved that I was deceiving myself, this instrument being in fact a gauge, not of tension, but of current. Only, indeed, did I begin to arrive at satisfactory results when, not long ago, I became possessed of the New Quadrant Electrometer of Sir William Thomson, together with the means for measuring the resistance of animal tissues to electrical conduction, for it was only when I began to work with these instruments that I was able for the first time to distinctly realize the facts with which I had to do, and for which I had been groping almost in the dark previously.

Working for myself with the instruments for measuring the resistance of animal tissues to electrical conduction, the fact, which I had not before sufficiently apprehended, became impressed upon me that these tissues might take rank under the head of non-conductors rather than under that of conductors.

I found, for example, that the resistance of an inch of the sciatic nerve of a frog was not less than 40,000 B. A. units — as much, that is, as eight times that of the whole Atlantic cable.

Seeking for tensional phenomena of animal electricity in muscle and nerve by means of the new quadrant electrometer, I soon found that the sides and ends of the fibres were charged differently, the former positively, the latter negatively, and that these

PREFACE.

evidences of charge disappeared in great measure during action. I soon found the evidences of the charge for which I had searched before almost in vain ; but I found more than I expected. Expecting to find a single charge I found a double charge ; and what to think of this state of things I could not at all see at first. The facts would not chime in with preconceived conceptions, and the end was that the conceptions had to be modified to suit the facts.

The view I had entertained almost from the very beginning of these investigations was that in some way or other the natural electricity present in muscle during rest produced the state of rest by keeping the muscular molecules in a state of mutual lepulsion, and that muscle contracted when this electricity was discharged, by virtue of its elasticity, the muscular molecules being then left free to obey the common attraction which is inherent in their physical constitution. The idea was that the muscular fibies were charged with one kind of electricity during rest, and that in this way the molecules were kept in a state of mutual repulsion. The idea was one which it was difficult to reconcile with the fact that there was a double charge of electricity in muscle. It was one which would agree well enough with the presence of a single charge, whether positive or negative ; it was one which seemed to clash altogether with the double charge, seeing that the mutual repulsion of molecules arising from the presence of either charge would be counteracted by the mutual attraction of molecules charged differently. What then ?

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Did the natural electricity present in the muscle produce the state of muscular relaxation and elongation in a different way ? Was it possible that the great resistance of animal tissues to electrical

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conduction might have an all-important part to play in the process under consideration ? Was it possible that the sheaths of the fibres in muscle might be so wanting in conductibility as to allow them to act as dielectrics ? Was it possible that, the sheaths being dielectrics, a charge of one kind of electricity developed on the outsides by the reactions of the blood there circulating, or in any other way, might induce a charge of the other kind of electricity on the insides, and that the electrical antagonism of the sides and ends of the fibres might be accounted for by the charge induced on the insides being conducted to the ends by the contents of the sheaths ? Was it possible that the fibres might be kept in the state of relaxation or elongation by the compression of the sheaths arising from the mutual attraction of the two opposite charges, disposed as in a charged Leyden jar, upon the two surfaces of the sheaths ? These were the questions which in turn presented themselves to my mind, and which, as it seemed, required to be answered in the affirmative. The idea was definite and fiee fiom many objections attaching to the idea whose place it had taken. It accounted for the difficulty of detecting the charge present in the fibre, and for the fact that the fibre could keep its charge through itself uninsulated ; for the two charges, disposed thus Leyden-jar-wise, upon the two opposite surfaces of

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ix the sheath of each fibre, masked each other, and at the same time imprisoned each other, just as they do in the ordinary charged Leyden jar. It was also an idea definite in this particular — that all the tensional phenomena of the muscular fibre, and all the currrent phenomena too, could be easily imitated upon a wooden model of the fibre, left bare at the two ends, and sheathed at the sides with a coating formed of two layers of tinfoil separated by an intermediate layer of thin gutta-percha sheeting, if only a charge was supplied to the outer layer of tin-foil. And in this also was the idea definite— that the elongation of the fibre, assumed to be brought about by the mutual attraction of the two opposite charges disposed Leyden-jar-wise upon the two surfaces of the sheath, was found to be reproducible on a narrow band of india-rubber covered on its two surfaces with a thin metallic coating so as to allow of its being charged as a Leyden jar is charged ; for, on thus charging, this band was seen to elongate under the mutual attraction of the two charges disposed upon its surfaces, just as the sheath of the muscular fibre is supposed to do. Nay, by this apparatus everything that is supposed to happen in muscular motion can be fully illustrated, contraction as well as relaxation, for this band, which had elongated under the charge, is seen to contract when this charge is discharged.

Nor does the galvanometer tell all that has to be told of what happens when animal tissues are included in the voltaic circuit. It tells of the voltaic current ; it does not tell of the charge which, under

X ordinary circumstances, . is associated with this curlent. It does not tell, as does the electrometer, that the parts between the poles are charged, half positively, half negatively, the former half being on the side of the positive pole, the latter half on the side of the negative pole. And yet this is information which cannot be dispensed with ; for, as will be proved in due time, the workings of voltaic electricity upon muscle are found to be resolvable into those of the chaige and discharge of these very charges, and not into those of the constant current. As with the workings of animal electricity, indeed, so here, the key is to be found in the revelations made by the electrometer rather than in those made by the galvanometer.

In a word, the result at which I have arrived is that the workings of all kinds of electricity, artificial and natural, upon muscle, are resolvable into those of charge and discharge, the charge elongating the fibres, the discharge of this charge bringing about the state of contraction, while at the same time strong confirmation of the view taken of the way in which the charge and discharge operate is found in the history of electrotonus (a subject now gone into for the first time), for there is every reason to believe that the increased contraction which is met with in electrotonus, and which is referred to “ exalted irritability,” is nothing more than the return of the fibres, by virtue of their elasticity simply, from a previous state of increased elongation, which state of increased elongation, now-pointed out for the first time, may be the

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xi necessaiy result of the sheaths of the fibres being more highly charged, and therefore more compressed, than they are naturally, by the charge imparted to them in electrotonus. All this and more will appear in its proper place and in due time ; indeed, the subject is only glanced at now in order to show that there is much new matter behind, and that the electrometer does really give a new key to the interpretation of these matters.

Nor is it otherwise with the problem of sensation. On the contrary, the electrometer is still the instrument which sheds light upon the phenomena to be dealt with rather than the galvanometer, and, in short, all, or nearly all, the conclusions arrived at respecting the action of electricity, natural and artificial, upon muscle, are found to be applicable in this case also.

For the rest, I must only say broadly that the general view of the dynamics of nerve and muscle proves to be in strict accordance with this partial view, and not with the view which assumes that muscle and nerve have a special life which expresses itself in contraction or sensation, as the case may be. The action of the blood upon muscle, when it is enquired into fully, is found to be one which antagonizes muscular contraction rather than causes it. The case is not one in which excess of blood in the parts which have to do with the production of motion shows itself in excess of muscular contraction, as it would do if this latter excess were, as it is assumed to be, expressive of heightened life, but it is in every way the reverse of this.

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The blood, in fact, would seem to act as does the natural electricity, producing rest rather than action — producing rest, it may be, by keeping up the natural electricity of the parts. And so likewise with the action of “ nervous influence ” in the production of muscular motion and sensation. The case is one in which it is far more easy to believe that muscular action and sensation are produced by the abstraction rather than by the communication of this influence— one which accords more readily with the idea that nervous influence, like the natural electricity, acts by antagonizing action in muscle and nerve — acts, it may be, through the natural electricity of the parts. The facts are all in harmony, not with the view which looks upon action in muscle and nerve as the expression of the special life with which muscle and nerve are supposed to be endowed, but with the view which is based upon the notion that there is along with the state of rest a state of charge, and that the change from the state of rest to that of action is brought about by the discharge of this charge ; and with this general statement I must content myself, for the few preliminary words which are here permissible would not serve to give any clear idea of the subject as it presents itself in detail.

CONTENTS .

DYNAMICS OF NERVE AND MUSCLE.

PART I. The Subject from a Physiological Point of View

page

Chapter I. On some preliminary particulars respecting animal

electricity ..

Chapter II. On the electrical phenomena belonging to living nerve and muscle (luring the state of rest ... ... - - •

Chapter III. On the electrical phenomena which mark the passing of nerve and muscle from the state of rest into that of action

Chapter IV. On the history of the so-called “inverse ’’and “direct” currents, as indicating the way in which muscular

motion is affected by voltaic electricity

Chapter V. On the history of electrotonus, as indicating the way in which muscular motion is affected by voltaic electricity Chapter VI. On the way in which sensory nerves are affected

by voltaic electricity

Chapter VII. On the way in which nerve and muscle are

affected by electricity in general

Chapter VIII. On the action of the blood in tire production

of muscular motion

Chapter IX. On the action of nervous influence upon the muscles

Chapter X. On the phenomena of rhythmical muscular action

as elucidating the action of nerve and muscle

Chapter XI. On the nature of muscular action

Chapter XII. On the nature of rigor mortis

Chapter XIII. On the nature of nervous action i

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PART II. " The Subject from a Pathological Point of View

page

Chapter I. On the history of muscular motion as exhibited in

epilepsy and other forms of convulsion ... ... ... ••• 209

Chapter II. On the history of muscular motion as exhibited in common trembling and other forms of tremor ... ... ... 235

Chapter i. ON SOME PRELIMINARY PARTICULARS RESPECTING ANIMAL ELECTRICITY

SHORT time before the close of the last centuiy the illustrious author of “ Cosmos” wrote :* “ Le nom de Galvani ne perira point; les sRcles futurs profiteront de sa decouverte, et, comme le dit Brandes, ils reconnaitront que la physiologie doit Galvani et a Harvey ses deux bases principales.” This is saying much, but, as I believe, it is not saying more than what is now fully borne out by the facts ; and on this account I think it will not be waste of time to take a cursory glance at the history of the discovery of animal electricity before proceeding to deal with problems in which, as I hope to show before I have done, this agent supplies us with the master key.

The discovery of animal electricity dates as far

* “Experiences sur le galvanisme, et en general sur 1’irritation des fibres musculaires et nerveuses.” F. A. von Humboldt, Traduit par J. F. N. Jadelot. 8vo. Paris, 1799, p. 361.

B back as 1786. One day in the course of this year, while amusing himself with a common electrical machine near a dish on which lay a number of frogs’ legs prepared in the way in which it is usual to prepare them for purposes of cookery, Galvani, seeing that these limbs jumped whenever he drew a spark from the primary conductor, was led to think that discharges of atmospheric electricity might make themselves known by similar jumpings. Needing a more delicate electroscope than the one he then had in order to carry on some investigations in atmospheric electricity with which he was then engaged, and wishing to know whether he had found what he needed, he at once took the dish, with its contents, and went out of doors, his nephew, Camillo Galvani, who was with him at the moment, going with him. The time was a clear and calm evening in September. It did not promise success, for the sky was free from all signs of electrical disturbances : it proved to be propitious in an unexpected direction. The place was a high terrace belonging to the house at Bologna in which Galvani lived — then the Casa Panfili-Colonna, now the Casa Monti, in the Strada S. Gervasio. The house, the terrace, the railings, are still to be seen at No. 96 in the Strada S. Felice, the only change of moment being in the name of the street. Each pair of limbs was suspended by a small iron hook from the horizontal bar of the iron railings which fenced in the highest part of the terrace, the hook transfixing the portion of spine which had not been cut away. Galvani says “ Ranas itaque consueto more paratas uncino ferreo earum spinali medulla perforata atque appensa, sep-

NERVE AND MUSCLE.

tembris initio (1786) die vesperascente supra parapetto horizontaliter collocavimus. Uncinus ferream laminam tangebat ; en motus in rana spontanei, varii, haud infrequentes ! Si digito uncinulum adversus ferream superficiem premeretur, quiescentes excitabantur, et toties ferme quoties hujusmodi pressio adhiberetur.”* How, then, were these contractions to be accounted for ? They could not be due to discharges of atmospheric electricity, for the sky presented no indications of electric disturbance : they could not be due to the sparks which gave rise to them within the house, for the electric machine, which had also been left behind, was not in action : they could not be due, that is, to discharges of either of the two kinds of electricity then known. Could there be electricity in the limbs themselves, and were the contractions the consequences of the workings of this agent? Were the contractions arguments in favour of the existence of animal electricity ? From this time until the day of his death, Galvani went on performing experiment after experiment, sacrificing hecatombs of frogs, always firm in his belief that these questions ought to be answered in the affirmative, and unceasingly striving to bring others to the same mind with himself. He was, however, destined to be foiled, and that, too, by a weapon which lay hid in one of his own experiments. The experiment in question was one in which a galvanoscopic frog was thrown into a state of momentary contraction by placing a conducting arc, of which one half was silver and the other half copper, between the * “De Viribus Elcctricitatis in Motu Musculari Commentarius. ”

lumbar nerves and the crural muscles* Galvani, as was his wont, explained these contractions by supposing that the conducting arc had served to discharge animal electricity, and that the contractions were the result of the discharge. Volta, on the other hand, was of opinion that the electricity producing these contractions originated in certain reactions between the silver and copper portions of the conducting arc ; and he was not shaken in this view by what he did afterwards, for, wishing to confirm it, he began a series of investigations which ended in the discovery of the voltaic pile and battery — a discovery which filled all minds with wonder, and for a long time afterwards diverted attention altogether from the consideration of the claims of animal electricity. In the meantime, however, while Volta was demonstrating the existence of that electricity which originates in the reaction of heterogeneous bodies, and which is now known as voltaic electricity, Galvani continued his search after animal electricity, and made many important discoveries as he went along. He discovered, among other things, that a galvanoscopic frog would contract without the help of a conducting arc composed of heterogeneous metals. He discovered not only that these contractions would happen when this arc was composed of a single metal, but also that an arc composed of muscle or nerve would answer the same purpose as the metallic arc. He also discovered that the limb of a galvanoscopic frog, of which the nerve had been divided high up in the

* The galvanoscopic frog was prepared from the hinder half of the animal, by stripping off the skin, and cutting away all the parts between the thighs and the fragment of the spine, except the principal nerves.

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loins, would contract at the moment when the end of the nerve below the line of division was brought down and made to touch a part of the trunk of the same nerve. At last, indeed, he hit upon an experiment in which he seemed to have to do with an electricity other than that arising from the reaction of heterogeneous bodies — an electricity which must belong to the animal tissues themselves. He did much, but he did not do enough to win the battle in which he was engaged, for Volta still kept his position, denying the existence of animal electricity, and maintaining that the electricity which produced the contractions in the galvanoscopic frogs was always due to electricity arising in the reaction of heterogeneous bodies of one kind or other — silver and copper, metal and organic tissue, muscle and nerve, nerve in one state with nerve in another, as the case might be.*

In 1799, Humboldt took up the question at issue between Galvani and Volta, and published a workf in which he shows by many new and curious experiments that there was error on both sides — that Volta was wrong in ignoring altogether the influence of animal electricity in Galvani’s experiments, and that Galvani was not less wrong in recognising nothing but this influence. He, himself, as is proved in the extract already given, was a firm believer in animal electricity ; but he failed to supply reasons for this belief which can be thoroughly satisfactory to others. Still, he did something in this direction by making out — first, that the agent assumed to exist and to be animal electricity has this in common with

* “Ann de Chim.,” t. xxiii., p. 276 and 301. f “ Op. Oil.”

electricity, that its action is permitted by conductors and prevented by non-conductors ; and, secondly, that it is not to be confounded with voltaic electricity, because the action, which is permitted by conductors, is possible across a gap in the circuit which would allow the passage of frictional electricity, but which would altogether prevent that of voltaic electricity — which would, that is to say, allow electricity of high tension to pass, but not electricity of low tension. What Humboldt did, in fact, was to increase the probabilities of the existence of animal electricity not a little, and at the same time to make it appear that this electricity would prove to be of higher tension than voltaic electricity.

In 1803, Aldini, Galvani’s nephew,* published an an account of certain experiments which furnish further evidence in favour of the existence of animal electricity, by showing that living animal tissues are capable of giving rise to attractions and repulsions which seem to be no other than electrical attractions and repulsions. “ I held,” he says, “ the muscles of a prepared frog in one of my hands, moistened with salt and water, and brought a finger of the other hand, well moistened in the same way, near to the crural nerves. When the frog possessed a great deal of vitality, the crural nerves gradually approached my hand, and strong contractions took place at the moment of contact.” And again : — “ Being desirous to render this phenomenon more evident, I formed

* “ Account of the late Improvements in Galvanism, with a series of curious and interesting experiments performed before the Commissioners of the French National Institute, and repeated in the Anatomical Theatres of London, &c. ” 4to. London, 1803.

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the arc by applying one of nay hands to the spinal naarrow of a warm-blooded animal, while I held the frog in such a manner that its crural nerves were brought very near to the abdominal muscle. By this arrangement, the attraction of the nerves of the frog became very evident.”

About this time, however, the. discovery of the voltaic battery had given the victory to the opinions of Volta — a victory so complete that nothing more was heard about animal electricity for the next thirty years.

In 1827, Nobili* brought back the subject of animal electricity to the thoughts of physiologists by discovering an electric current in the frog. He made this discovery by means of the very sensitive galvanometer which he himself had invented a short time previously — an instrument which, as perfected by M. Du Bois-Reymond and others, by Sir William Thompson more especially, ought to be as prominent an object as the microscope in the laboratory of every physiologist. Immersing each end of the coil of the instrument in a vessel containing either simple water or brine, and completing the circuit between the two vessels with a galvanoscopic frog, — the fragment of the spine being immersed in one vessel, and the paws in the other, — he found that there was a current in the frog from the feet upwards, which current would cause a considerable permanent deflection of the needle, — to 30° or more if brine were used, to io°, or thereabouts, if water were substituted for brine. Nobili supposed that this current was peculiar to the frog, and in this he erred ; but he did, nevertheless, a great thing, for, [by this experiment, he furnished, perhaps, the first unequivocal proof of the real existence of animal electricity.

Twelve or thirteen years later, Matteucci published an essay* which, as M. de la Rive says,t “ restored to anynal electricity the place which it ought to occupy in electrical and physiological phenomena.” This essay, moreover, had a great indirect influence upon the fortunes of animal electricity, for M. Du Bois-Reymond, as he himself tells us, was led to undertake the investigations which have made his name famous in this department of physiology by the inspiration arising from its perusal.

The joint labours of MM. Matteucci and Du Bois- Reymond have left no room for entertaining any doubt as to the reality of animal electricity. This will appear sufficiently in the sequel, when many of the experiments which furnish the demonstration will have to be referred to particularly. In the meantime, it may be said that Manteucci has demonstrated in the most unequivocal manner that animal electricity is capable of decomposing iodide of potassium, and of giving “signes de tension avec un condensateur dclicat,”f as well as of producing movement in the needle of the galvanometer ; and not only so, but also — a fact, the discovery of which

f “ A Treatise on Electricity, in theory and practice. Translated by C. V. Walker.” 8vo. Longman. 1853-1858.

J “ Cours d’Electro-physiologie.” Paris. 1858.

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will always give Matteucci a place in the very foremost rank of physiological discoverers — that musclar contraction is accompanied by an electrical discharge analogous to that of the Torpedo, And as for M. Du Bois-Reymond* it may be said that he has demonstrated that there are electrical currents in nerve — in brain, spinal cord, and other great nerve-centres, in sensory, motor, and mixed nerves, in the minutest fragment as well as in masses of considerable size,' — that the electrical current of muscle, which had been already discovered by Matteucci, may be traced from the entire muscle to the single primitive fasciculus, — that Nobili’s “ frog current,” instead of being peculiar to the frog, is nothing more than the outflowing of the currents from the muscles and nerves, — that the law of the current of the muscle in the frog is the same as that of the current of the muscles in man, rabbits, guineapigs and mice, in pigeons and sparrows, in tortoises, lizards, adders, glow-worms, toads, tadpoles, and salamanders, in tench, in freshwater crabs, in earthworms— in creatures belonging to every department of the animal kingdom, — that the law of the current in muscle agrees in every particular with the law of the current in nerve, and also with that of the feeble currents which are met with in tendon and other living tissues, — and that there are sundry changes in the current of muscle and nerve under certain circumstances, as during muscular contraction, during nervous action, under the influence of continuous and interrupted galvanic currents, and so on, which changes,