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only in complexity from those exhibited in the non-living causative explanation, would be immediately abandoned if world, and impelled by this reluctance he fabricates for the phenomena were subsequently found to be explicable them, out of his own conceit, a special and exclusive on physical and chemical conceptions. Biotic energy realm. The logical pressure of physical and chemical

appears to as only an intellectual compromist, an conceptions forbids the postulation, by either the public abortive attempt to clothe the naked form of sitalism in or the neo-vitalist, of such an incongruous entity as a a decent scientific dress; but, although partially clothed, vital chemical element capable of blending with the familiar it offers, like neo-vitalism, no new method for physio chemical elements recognised in the material world ; yet logical investigation, and must, in consequence, remain the physiological processes of life are in popular estim- barren, never contributing towards physiological achieveation still held to be due to peculiar forces blending with To what extent its adoption may be an intellectual those of the material world, but so essentially different solace is a question which does not fall within the scope that they can only be described as “ vital." The neo- of physiology. Certain physiological phenomena are vitalistic school of men of science, without adopting this especially brought forward as necessitating the assumption popular view in its entirety, retains the same term for of vitalistic or biotic conceptions; among these are the such physiological characteristics of cell processes as, with phenomena of nervous activities, the formation and activiour present limited knowledge and with our present in- ties of enzymes, and the passage of substances through adequate methods of investigation, seem to be in disagree- living membranes. The question of the nervous activities ment with present chemical and physical conceptions. will be dealt with later ; but as regards the diffusion of This disagreement is accentuated by the assumption of gases or substances in solution through cellular membranes directive vital forces, and since these cannot be ranged a few general considerations may be advanced now.' The alongside those of chemistry and physics, transcendental passage of substances into and through non-living memphenomena may be always expected to occur the orderly branes is modified in regard to both the velocity and the array of which as part of natural science is not merely selective character of the passage by a large numbrt of a futile but on a priori grounds an absolutely impossible factors, among which are nature of substance, pressure, task. In order to justify this description as representing osmotic index, temperature, and the structural, electrothe views of some neo-vitalists, I will quote a few sentences lytic, and chemical characters of the membrane. Tissue from the presidential address delivered in 1898 by Prof. membranes, whether animal or vegetable, possess a comJapp in the Chemical Section of this Association. This plicated particulate structure, and it is obvious that experiaddress dealt with the formation of the optically active ments must be carried out extensively on dead tissue mer. substances found in vegetable and animal tissues or their branes in order to determine how far the general particulate extracts. It asserts that “the absolute origin of com- arrangement may modify the rate and character of the pounds of one-sided symmetry to be found in the living passage. In this respect our present information is not world is a mystery as profound as the origin of life itself. sufficiently extensive to warrant any definite general stateIn regard to this it may be remarked that the absolute ment, and such experimental evidence as exists opens up origin of anything, living or non-living, is a mystery difficult problems in molecular physics which still await which science does not attempt to solve, relative not solution ; moreover, the presence of electrolytes, by assist. absolute causation being the object of scientific grouping, ing adsorption, appears to modify the apparent rate and hence this assertion does not necessarily imply any funda- character of the total passage, and further experiments are mental distinction between the two classes of phenomena. necessary on this point. But in the living membrane, But there is more than appears upon the surface, for the especially when it is composed of cellular units, the whole whole argument leads up to the sweeping statement that question is additionally complicated by the great prob

no fortuitous concourse of atoms, even with all eternity ability that the cells are the seat of chemical processes for them to clash and combine in, could compass this the nature of which is imperfectly known; such processes feat of the formation of the first optically active organic constitute the metabolism of the cells. It would, therefore, compound.” It is thus inferred that because the manner be somewhat surprising if the phenomena of the passage of such formation cannot be accounted for in the present of substances through such cellular membranes were in condition of scientific knowledge, its scientific causation is strict accord with the passage of similar substances through from the nature of things unknowable. However, although non-living membranes which have not the same particulate unknowable in the strictly scientific sense, the intellectual framework and are not the possible seat of similar chemical craving for causative explanation of some sort urges Prof. processes. The statement, therefore, that any discrepancy Japp to say, “I see no escape from the conclusion that between the two classes of phenomena necessitates the at thr moment when life arose a directive force came into assumption of a peculiar vital directive force disrrgards play. There is here introduced a grandiose term for life

the circumstance that between the conditions in the one which is viewed as involving directive forces; the term, case and those in the other lies a large and little explored however, adds nothing to our physiological knowledge, is field; moreover, such a statement implies, without any not in itself explanatory, and not only offers no warrant, that any physico-chemical explanation must method of physiological investigation, but brands as use- necessarily be insufficient in the case of the living memless all the methods derived from physics and chemistry, brane, although it is realised that there may be active past, present, and future. In a recent work Prof. Moore chemical processes of the operations of which we have at has attempted to set forth a conception which shall be present little exact knowledge. vitalistic in essence, and yet not so completely out of touch What possible justification is there, therefore, for brand. with the principles of natural science.'' He regards living ing as hopeless all further physical and chemical investicells as transformers of energy and thus leaves them abso- gation of certain aspects of the phenomena by attributing lutely dependent upon its receipt ; the transformed mode these to vital directive forces? The gaps and imperfections which is achieved by the cells is, however, one which of the palæontological record were triumphantly vaunted cannot be interpreted in terms of the familiar modes pre- by the opponents of evolution ; and now that the work of sented in the non-living world. He terms the transformed successive years has convincingly contributed towards the mode “biotic energy, and the distinction between this filling up of these gaps not only has this objection caland vital directive force" appears to be its absolute lapsed, but the hypothesis of special creations which it dependence upon the other modes for its appearance. It supported has been involved in its fall. There are indicathus does not run counter to the law of the conservation tions that the discrepancies in diffusion phenomena through of energy, and warrants, in the opinion of some, the con- widely different structures may be knit by the results of fident expectation that it will be found capable of precise experiment on intermediate modifications. It may be mans scientific expression. I confess that I am unable to share this confidence. The introduction of the conception entails 1 The conception of Ostwald as to the action of catalytic subatonces the same double terminology to which I have referred,

extremely suggestive in connection with the activities of enzymes, both in and I feel convinced that the assumption, in the case of

tracellular and extracellular. It is possible that the changes i pouzhtamat

hy enzyınes may, with the growih of our knowledge in physical chemary any given physiological phenomena, of biotic energy as a be shown to be of the same order as those which slowly occur in the air

of enzymes, and that the enzyme it-ell by facilitating adsorption pheroma I See article by B. Moore in “Recent Advances in Physiology and Bio- may merelv act by accelerating the veloci'y of the special chang chemistry." Edited by L. Hill, F.R.S. (London: Arnold, 1906.)

Leathes, " Problems in Animal Metabolism“ (London : Murray, 1904)

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years before these are completed, but the introduction of wealth of material I select one of great importance and vitalisın or biotic energy as a fictitious causative explan- promise. It is that of the constitution of the nitrogenous ation is so opposed to the spirit and the progress of science compound familiarly known as proteid, which from its that we may safely predict the complete abandonment of close association with protoplasm, the physical basis of life, this position at a comparatively early date.

has a fundamental significance and has therefore attracted I venture now to define my own position in regard to the attention of many competent investigators. Important this matter. I assert that, although the complexity of researches have been made on this subject by physiological living tissues makes our present knowledge extremely chemists, notably Hofmeister and Kossel, and at the prelimited, it is essentially unscientific to say that any physio- sent time the subject is also being studied by one of the logical phenomenon is caused by vital force or is an argu-ablest organic chemists of the day, Emil Fischer, whose ment in favour of " vitalism," and that, if this phraseology previous work on carbohydrates is so illuminating.' In is offered as a sufficient description of the phenomenon, the splendid chemical laboratory at Berlin, with its unils further scientific study is prejudiced because the only paralleled equipment, a succession of researches have been terminology which admits of scientific exactitude is

carried out dealing not only with the constitution of the excluded. I assert, further, that if the term vitalism simpler proteid derivatives, but also with the important coanotes no more in physiology than the term “ living, and difficult problem of the synthetic grouping of these its employment does not in any way enlarge our intellectual derivatives into more complex compounds. The success view of the subject-matter of physiology, and can only which has so far attended these investigations is so probe considered either as meaningless tautology or

nounced as to encourage the hope that the future may expression of faith; but if the term has some additional, reveal the chemical constitution of proteid itself and thus occult, and mystic significance, then its employment is bring us perceptibly nearer to its possible synthetic formdetrimental to the progress of physiology, exerting as ation. We congratulate ourselves that this problem has at abstructive an influence upon the growth of our science last attracted the earnest attention of organic chemists. as the conception of special creation exerted upon the I now invite your attention to those further aspects progress of biology.

indicated in the opening sentence of this address, which Vitalism is not the only “ism” which, perhaps unwittingly, obstructs physiological progress; it is, however,

imply the presence of automatic mechanisms by which the

various processes of the body organs are regulated and far more worthy of respect than others which I do not coordinated for the welfare of the whole organism. propose to particularise, for it is a twig of that lusty tree Many such automatic mechanisms are now known. which, in philosophy, still claims the largest share of Some of these are of an obvious chemical type, the men's belief. The vitalist, leaving the more solid ground mechanism being the production in minute quantity of of physics and chemistry, enters the realm of metaphysics chemical substances which are conveyed to remote organs and there attaches himself to that distinguished circle of

by the circulating blood. In this way adrenalin, a subidealists whose pedigree extends back to Plato. If, as

stance elaborated by the medullary portion of the supramay be asserted with great confidence, idealism in philo- renal organs, augments the activities of the muscles, parsophy will endure as long as thought exists, then it might ticularly those of the arterioles.

From his recent be expected that vitalism in physiology will never entirely searches Langley 2 is disposed to believe that many cease. The history of physiology, however, reveals the chemical compounds which augment or diminish the luctuating extent of its influence. Potent a century or activity of muscles and glands do not act by altering the more ago, vitalism nearly disappeared between 1850 and differentiated tissue, but play upon a hypothetical receptive 1870 under the pressure of the application of physical and substance which lies at the junction of the tissue with its chemical methods to physiology; it revived again towards

entering nerves. This middleman, so situated as

to lie the century's close, the ripple of a wide-spreading wave of idealistic philosophy.

in the interstices of the neuro-muscular junction, bears a Materialism and idealism have

relation to the muscle or gland-cell somewhat analogous been described by Huxley as appearing in the history of

to that which the fulminating cap bears to the cartridge, philosophy like " the shades of Scandinavian heroes

and it is quite conceivable that it is maintained in an eternally slaying one another and eternally coming to life again." As a physiologist, I do not

appropriate condition of instability or explosiveness by the to touch

direct action of chemical substances conveyed to it in however lightly upon this metaphysical duel, since I frankly

minute amounts by the blood. admit my own incapacity to do so and the particular

It is remarkable how many of these strictly chemical applicability to my own powers of the words of Gibbon

automatic mechanisms have been discovered in the last that “it is much casier to ascertain the appetites of a quadruped than the speculations of a philosopher.

few years, thus substantiating the views of Brown-Séquard. It is

The automatic character of the mechanism which detertherefore without any intention of casting any suspicion

mines the secretion of the pancreatic fluid was revealed by of doubt upon the confidence felt as to the persistence of idealism in philosophy that I suggest that neo-vitalism

the experiments of Bayliss and Starling, which showed in physiology bears upon its surface the signs of its own

that definite chemical compounds are formed in the lining

cells of the small intestine, and that treatment with weak decay. One such sign is the circumstance that even its

acid, such as occurs in the acid chyme, liberates a submost ardent exponents refuse to follow the lead of this

stance which, absorbed into the blood, has the special ignis fatuus, but assiduously investigate living processes by the most improved chemical and physical methods ;

function of stimulating the pancreatic cells. A similar

automatic mechanism has been found by Edkins to exist another is that when any so-called vitalistic aspect of some

in the stomach, for although the flow of gastric juice is physiological phenomenon is rendered explicable on physical initiated by nervous channels, the subsequent peptic secreand chemical lines, the vitalist abandons in this instance

tion is largely augmented through the presence in the his peculiar standpoint. Neo-vitalism has of late thus lost

blood of chemical substances elaborated and absorbed in nts corrosive character; it now spreads as a thin but

the pyloric portion of the stomach wall.“ Marshall and tenacious film over physiological conceptions and is in this Jolly have recently shown that substances elaborated in way mildly obstructive, but its obstructive viscosity is con

the maternal ovaries, and particularly in the tinually yielding to the accumulating mass of the more precise knowledge which it endeavours to obscure.

luteum, determine, when introduced into the circulating Re

blood, the changes necessary for the proper attachment of Search along physical and chemical lines into physiological the embryo to the uterine wall and thus the further developprocesses is its uncompromising opponent, so that there is ment of the embrvo during the first stages of pregnancy. Every reason for believing with Huxley that the weight

The researches of Starling and Miss Lane-Claypon indicate and increasing number of those who refuse to be the prey of verbal mystifications have begun to tell.

IF. Fischer, Berichte Deutsch. Gesellschaft, xxxviii. 1905. (See also The recent history of physiological progress shows that

“La synthèse des matières protéiques,” par L. C. Maillard. investigations confined to the study of physical and chemical

Générale des Sciences Févr. 1006 Paris.)

2 J. N. Langley, Journ. of Physiol., xxxiii. 1905, p. 374, and Croonian processes have been the one fruitful source of physiological Lecture. Roy. Soc., 1906. knowledge. It would be impossible to give even a brief

3 Pavliss and Starling, Journ. of Physiol., xxviii. 1902, p. 325. survey of the chief results which have, during the last

4 Fdkins, “On the Chemical Mechanism of Gastric Secretion," Proc.

Roy Soc. B. lxxvi., 1905, p. 376. twenty years, been thus obtained. Out of the enormous 5 Marshall and Jolly, Phil. Trans. Roy. Soc. London, B, 1905, p. 198.

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that chemical substances formed during pregnancy in the

of one such cell. This neuron theory is based upon tissues of the fætus will, if introduced into the maternal developmental history and upon the suggestive fact that blood, directly evoke the appropriate activities of the re- each nerve cell forms an independent trophic centre for its mote mammary glands."

own distributed processes. It is undoubted that, like the These are only a few instances of a class of mechanisms, atomic theory in chemistry, the neuron theory has proved strictly chemical in character, by which the activities of of enormous service, enabling neurologists to disentanglr remote and dissimilar organs are automatically coordinated ; the woven strands of nerve-cell processes even in such an a further class of such mechanisms, although involving a

intricate woof as that of the central nervous mass. Thrre chemical substance conveyed by the blood, carries out the are, however, difficulties associated with its full accepiactual regulation by means of the central nervous system. ance in physiology, as indeed there are said to be in conAn example of this class is afforded by the researches of nection with the full acceptance of the atomic theory in Haldane and Priestley upon the carbonic-acid gas in the chemistry; but dismissing these for the moment, I pass on pulmonary air. These show that the alveolar pressure of to consider the presumable character of such a conception carbonic acid in the lung spaces remains constant even of nervous activities as would be demanded on the sup when the atmospheric pressure is considerately altered in position that the nervous system is, as regards all essentials amount. The constancy is due to the circumstance that an automatic physicochemical mechanism. the respiratory nerve centres are exquisitely sensitive to a In the nerve fibres, which are undoubtedly the offshoots rise in this carbonic-acid pressure. Any such rise slightly of nerve cells, the only demonstrable changes during the augments the carbonic-acid tension of the pulmonary actual passage of nervous impulses are of an electrical blood, which, on being conveyed to the nerve centres, type. These resemble the effects which would occur if arouses their greater activity, and the increased efficiency there were redistributions of such electrolytes as are known of the respiratory ventilation, thus produced, rapidly re- to exist within and around the differentiated fibrillaınd duces the amount of the very agent which is its exciting core or axon of each nerve fibre. All the better-knuun cause. The researches of Hill and Greenwood, with air aspects of nerve-fibre activities are in accordance with such pressures up seven atmospheres, bear out the con- an electrolytic conception. The exquisite sensibility of clusion that by this automatic mechanism the air in the

to physical and chemical changes of a sudden lung alveoli has a practically constant pressure of carbonic character would be associated with the Auctuating and acid in any given individual.'

variable character of electrolytic distribution, this instability The introduction, in this example, of the respiratory being characteristic of particular electrolytes in colloidal centres and nerves raises the question whether the nervous solutions; hence physical and chemical alterations primary system, which is in a very special sense the channel for affecting the nerve envelope will, by modifying the electrothe regulation and coordination of the various activities of lytic distribution, produce physico-chemical change in the the body, may not itself be conceived to be a supreme internal axon itself. Such changes, when once produced example of an automatic physico-chemical mechanism, the at any point in the differentiated fibrillar continuum of the transference from one part to another taking place, not nerve fibre, must in accordance with the conception first through the flow of blood containing chemical substances, propounded by Hermann be propagated or transmited along but through a more subtle physico-chemical flow along the This continuum. The redistribution of electrolytes all the highly differentiated nervous strands of which this system seat of the external impression being itself a source of consists. The nervous system is not popularly regarded in electromotive effects, electrical currents demonstrably few this light; on the contrary it is considered to be the special from this point into the contiguous parts of the fibrillar seat of vital directive forces, and it is held, even by some continuum. Such flow of current must reproduce in them scientific men, that the nervous energy which it manifests neighbouring continuum that electrolytic redistribution is so transcendental in its essence that it can

never be

which is the fundamental aspect of nerve-fibre actity. brought into line with those modes of energy prevailing Thus, by this comparatively simple automatic mechanism. in chemistry and physics. There is, moreover, a wide- the physico-chemical electrolytic change is successively spread belief, founded upon conscious volitional power,

assumed by the various portions which compose the Irngth that nervous energy can be spontaneously created, and of the differentiated axon, and the new or active phrase in that even if its manifestations are bound up with the propagated along a nerve fibre as infallibly as . fiume integrity of certain definite nervous structures, these struc- speeds along a fuse when one end is ignited; in this 135 tures only form the material residence of genii, temporarily the conception explains how a so-called nervous impuls in possession, endowed with the powers of hypothetical is brought into being. Further, the brief duration of thir homunculi at the bidding of which the manifestations activity of the nerve, its rapid development and slar; either take place or cease.

decline, and the circumstance that a second external chui The complexity of nervous structure and the apparently cannot arouse a second activity if it occurs very shorts uncertain character of

activities furnished the after an effective predecessor, all have their counterpur older writers with plausible reasons for assuming the exist- on the electrolytic side, and we have convincing aidesur ence of animal spirits, but the extensive researches of half that the electrolytic redistribution during activits cannot a century progressively suggest that nervous phenomena be again produced until the electrolytic condition has mor may be regarded as the sum of particular physico-chemical or less returned to its original resting poine : the real processes localised in an intricate differentiated structure, peculiarity of the living tissue is its persistent tendera y the threads of which are being unravelled by neurological to re-establish the electrolytic concentration of this restin technique. This chapter of physiology still bristles with poise.' Finally experiments show more and more on difficult problems and obscure points, yet the unmistakable vincingly that the capacity of the nerve to respond in trend of the immense advances which have been made in external changes, as well as the magnitude and duratia recent years is towards the assumption that nervous pro- of the aroused activities, are particularly suscepi ole lu cesses do not in their essence differ from processes occur- modification by all those agents which are most priomf ring elsewhere in both the living and non-living worlds. in affecting electrolytic aggregates, such as temperatur

As regards structure it is generally assumed by neuro- electrolysis, and impregnation with various electrolites logists that the whole system is a fabric of interwoven These electrical indications of nerve-libre activities 2* elements termed neurons, each with a nucleated nerve cell fundamentally the same whether the fibres occur in prata and offshoots, one of which may be extended as a nerve pheral nerve trunks or in the bundles which course through fibre, whilst no nerve fibre exists which is not the offshoot the central masses; and thus, if the whole srstem rao1 Starling and Lane.Claypon.

sisted of nothing but the united strands of differentiatre 2 Haldane and Priestley, “The Regulation of Lung Ventilation.” Journ. nerve fibres, nervous phenomena would be merely the pr. of Physiol.. xxxii. 1905. 3 Hill and Greenwood, “ The Influence of Increased Barometric Pressure

pression of the development, along appropriately distribuia on Man.” Proc Roy. Soc., vol. lxxvii B, 1006. p. 442.

tracts, of similar electrolytic changes primarily starte be + Lodge, “Life and Malter " (London: Williams and Norgate, 19-6). some external physical or chemical alteration. But adó "Matter is the vehicle of mind, but it is dominated and transcended by it tional complications are introduced by the existence of (p. 123). Contemplate a hrain-cell, whence originates a certain nerveprocess whereby energy is liberated with some resultant effect" (p. 168).

nerve-fibre endings and by the interposition of the nere "It is intelligence which directs; it is physical energy which is directed and controlled and produces the result in time and space" (p. 169).

I Gotch and Burch, Jonrn. of Pkysiol., vol. xxiv. 1899, p. 470

nervous

427

or

cells. According to the neuron theory the fibres of different which a succession oi centripetal impulses can force a Derve cells and inore or less blindly, and, at any rate in passage as opposed to the difficulty with which a single vertebrates, do not demonstrably unite at their termini such impulse does so-is not peculiar to the central mass, within the central mass; hence gaps exist at the junction but is observed more or less in peripheral nerve endings; unbridged by the differentiated structural continuum. But for instance, those of electrical organs. Finally, the results since the nervous impulse can pass from one set to the obtained by Wedenski suggest that anæsthetics have a ouirr, a physiological continuum undoubtedly exists; it is particular affinity for nerve endings, including the perinecessary, therefore, to assume cither that the electro- pheral ones in the muscles; and although the causation is lytic change in one neuron can by mere contiguity in space at present imperfectly known, it does not seem improbable arouse a similar change in a neighbouring neuron process, that they may act upon some such specific substance as or that a differentiated connection actually exists, but of that which is conceived of by Langley under the term such structural delicacy that it cannot be microscopically receptive. demonstrated. Recently several physiologists have stated All the phenomena hitherto described are thus not necestheir belief in such continuity : one of these, E. Pauger, sarily aspects of the activity of that particular mass which bases his view upon the admitted intracellular nature of constitutes the body of the nerve cell, but of nerve endings peripheral nerve endings in muscles, glands, epithelial with their fine arborisations. As regards direct electrical rlls, and electrical organs. Arguing from analogy, he evidence of electrolytic changes in these finer branches, it insers that the central nerve endings of one neuron prob- so happens that Nature has provided some nerve endings ably pierce and enter the cell processes of another neuron.' on such a magnificent scale that this evidence is readily Such a connection can be actually seen, as a pericellular obtained. In the electrical organs of fishes the essential plexus, in the ganglia of crustacea, and has been occasion- structure consists of a pile of numerous discs each invaded ally described as observed in higher animals. Whether by nerve endings, and the electric shock of the fish is the the central termini of neuron processes are in reality sum of all the electrical changes in this pile when an joined by extremely fine fibrillar filaments or whether they efferent nervous impulse reaches each of its component and blindly in mere juxtaposition, it is undoubted that the discs. Its potency is due to the number of these comfunctional synapsis presents peculiar features. The chief ponents, but in each single component it is of the same peculiarities of synaptic activities as distinct from the order as the electromotive change in a

nerve, and its activities of the nerve fibres are the following :-Marked character is such as might be produced by electrolytic retardation in the maximum rate of propagation; irre- redistribution occurring simultaneously in the immense ciprocity of conduction, which is favoured in the natural number of nerve endings which are present in each disc or homodromous direction, whilst in the unnatural of the electrical organ. Although displaying the peculiariheterodromous direction it is obstructed or completelyties of apparent delay, &c., just referred to, the general blocked; susceptibility to fatigue; special susceptibility to character of the shock of the organ is such as to warrant stimulation and impairment by definite chemical substances, the belief that electrolytic conceptions of nerve-fibre activity by strychnine, absinthe, anasthetics, &c.; the presence of can be extended to the activities of nerve endings. a resistance which diminishes rapidly when subjected to There remains that special part of the whole neuron the assault of a series of entering or centripetal nervous which is the effective source both of its development and impulses even when each member of the series is alone of its maintenance, the nerve cell. Continuity with a nerve quite powerless to force a passage. All these peculiarities cell is essential for the integrity of both the structure and are more or less demonstrable in all nerve endings, peri- the function of a nerve fibre, but it is undoubted that, in pheral as well as central, and are presumably, therefore, its turn, the nerve cell is also dependent upon the existrelated to the character of the propagation which occurs ence of its processes in an unimpaired state. Thus the in the finely-divided non-medullated twigs or

“ arborisa

cell suffers a change which comes on slowly but with great rions into which the nerve fibres break up in such end certainty if any part of the neuron has been mutilated, or ings, and possibly to some further " receptive substance if the cell has been shorn of some of its offshoots. That lying beyond the endings. The retarded propagation, it forms a special part of the conducting path is indicated showing itself by an apparent delay, occurs in the motor by the occurrence of intracellular and nuclear alterations nerve endings of muscles and in the multitudinous nerve when a prolonged series of impulses travel towards it, and endings of electrical organs, as well as in the central a further more remarkable point is that it also appears to nervous system. Garten's researches on non-medullated change if the entering nervous impulses with their electroTrevés suggest that it may be connected with such slowed lytic concomitants are no longer able to reach it. This developinent of the electrolytic redistribution and of its suggests that nerve cells, far from being spontaneous accompanying electromotive alterations as is demonstrable

actors, are in a very real sense dependents; they form only in these structures.? Irreciprocity of conduction occurs one possible conducting portion of the whole differentiated where nerve endings are continued into muscle substance, tract, and atrophy when this tract is broken or is from since the activity process passes from nerve to muscle, but any circumstance not utilised. That the cell is primarily not the reverse way. In 1896 Engelmann succeeded by trophic and only incidentally a conductor is suggested by means of a double muscle-bath in so modifying one end Bethe's experiments upon crustacea. Owing to pericellular ol a muscle fibre that the wave of contraction, whilst it connections the actual nerve cell may be removed in these travelled freely along the muscle fibre from the unmodified animals without severing the whole conducting tract, for to the modified portion, would not do so the reverse way. a portion lies around but outside the cell ; and since, even The particular modification which produced this abnormal after such removal, the usual reflex movements of the supTasult is an interesting one ; it is the development of an plied antennæ are resumed, the cell cannot in this instance abnormally sluggish type of mobility, the whole activity be regarded as essential for the discharge of the motor of the modified region being greatly prolonged by means impulses which evoke the antenna movements. of veratria. This suggests that difference in the duration

In higher animals such removal of the cell body has ni the active process on the two sides of a central nervous

been imperfectly carried out by Steinach in the dorsal sinapain would, if present, be one factor in producing the spinal ganglia, but in the central mass it is impossible to well-known central irreciprocity. The susceptibility perform a crucial experiment of this kind so as to deterfatigue may be associated with this augmented difficulty of mine whether or no the substance of nerve cells can create propagation, and it undoubtedly occurs to a marked extent

nervous impulses. There are two particular features of in muscular nerve endings; for, according to the investi

reflex movements which may be cited as indicating that a Pations of Jotevko, it may be more pronounced in this motor nerve cell has at its call a store of nervous energy peripheral rnding than it is even in the spinal cord. Even

which it can spontaneously discharge. The first of these The w-called summation phenomena--that is, the ease with is the well-known fact that the character of reflex moveI E PAuger, “ Ueber den elementaren Bau des Nervensystems," Archiv

ments is such as to indicate the rhythmical discharge of ili Geo Phrstol. cxii., 1906.

groups of centrifugal nerve impulses the periodicity of 2 Garten, " Beitrige zur Physiologie der marklosen Nerven," Tena, 1903.

Engelmann, " Versuche uter irreciproke Reizleitung in Muskelfasern," Archit! Hie Ges. Physiol., leii, 86, p. 400,

1 Wedenski, “Erregung, Hemmung und Narkose," Archir' f. die Ges. Joleyko, " Travaux de l'Institut Solvay,” Bruxelles, iii. 2, 1900.

Physiol. c., 1993

Bethe, Allgemeine Anat. 16. Physiol. des Nervensystems, 1903, p. 99.
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which bears no relation to that of the centripetal ones. mechanism of inhibitory powers is remarkable both for its But it must be remembered that even in nerve fibres it is extent and its delicacy. It appears more and more probpossible for a succession of stimuli to evoke a different able that this is achieved by the propagation of nervous succession of electrolytic changes and of nerve impulses, impulses of the ordinary type. Thus, recent researches by provided that some of the successive stimuli fall within Sherrington show that the propagated impulses from a the period of inexcitability which occurs during the estab- given central mass may, although normally inhibitory to lishment of each new electrolytic poise.' We have, there- the centrifugal discharge of another mass, become directiy fore, only to assume, as is very probable, that in the incentive if the second controlling centre has its excitability central portion of the nervous path this poise is prolonged abnormally augmented by strychnine, tetanus loxin, &c.' in its development, and numbers of centripetal impulses As regards their fundamental characters it thus appears must necessarily fail; hence the emergent ones will have a that both augmenting and inhibiting impulses belong to special periodicity indicative of the duration of the swing the same category. Moreover, such theories of central of the electrolytic rearrangement which occurs when the inhibition as embrace all the phenomena involve as their synapses plus the cells traversed by the entering essential basis the cutting-ott of the potent centripetal impulse.

supply to the inhibited centre. in the interference thrury The second feature which more particularly suggests this cutting-off is assumed to be caused by the arrival of spontaneous celluiar activity is the well-known fact that other nerve impulses which, brraking into the path of reflex centrifugal discharges may continue after the obvious normal centripetal flow, obstruct and run counter to this centripetal ones have ceased. This is preeminently the case potent stream. In the ingenious drainage theory, prowhen the central mass is rendered extremely unstable by pounded by McDougall, the cutting-off is an indirect one, certain chemical compounds, such as strychnine, &c. ii being assumed ihat the new stream enters other side. There are, however, suggestive indications in connection channels, and thereby opens up a short circuit through with such persistent discharges. The more completely all which the potent ones drain away without reaching the the centripetal paths are blocked by severance and other centrifugal centre. Even Langley's conception of receptive means, the less perceptible is such persistent discharge, and substances played upon by impulses must be associated since nervous impulses are continually streaming into the

with a check in the efficiency of the continuous centripetal central mass from all parts, even from those in apparent

supply. repose, it would seem that could we completely isolate From the foregoing it appears that the physiologist has nerve cells, their discharge would probably altogether

definite grounds for believing that, as far as present know. In this connection a suggestive experiment was ledge goes, both the production and cessation of central carried out some years ago upon the spinal cord of the nervous discharges the expression of propagated mammal. A portion was isolated in situ by two cross- changes, and that these changes reveal themselves as sections, and a part of this isolated cord was split longi- physico-chemical alterations of an electrolytic character. tudinally into a ventral half containing the motor or centri- The nervous process, which rightly seems to us 30 fefugal nerve cells and a dorsal half containing the breaking

condite, does not, in the light of this conception, owe its up of the centripetal nerves; each half was then examined physiological mystery to a new form of energy, but to the for those electrolytic changes which indicate the presence

circumstance that a mode of energy displayed in the nonof nervous impulses. It was found that, even in the living world occurs in colloidal electrolytic structures of strychnised animal, no electrical effects could be detected great chemical complexity. There is a natural prejudice in the ventral half of the cord or its issuing roots, although

against the adoption of this view, but such prejudice should such effects were marked in the whole cord, and occurred surely be mitigated by the consideration that this full in the dorsal half which contained the centripetal nerve admission of physiology into the realm of natural science, fibres.

by forcing a more comprehensive recognition oi the This experiment indicates that even in the hyper-excitable harmony of Nature, is invested with intellectual grandeur. condition produced by strychnine the spinal motor nerve

With such questions as the essential meaning of concells did not discharge centrifugal impulses when cut off

sciousness and the interpretation of the various aspects of from their centripetal connections. It is corroborated by

mind revealed by introspective methods, the physiologist, the results obtained by Baglioni in the frog and small

as such, has no direct concern. For his purpose states of mammal,' and, taken in connection with those previously consciousness are regarded merely as signs that certain mentioned, it affords considerable foundation for assert- nervous structures are in a state of physiological activity; ing that the chief role of the nerve cell is trophic, and

and he thus limits the scope of physiology to the objective that, as regards issuing nerve impulses, it only forms a world. This limitation of physiology does not prohibit a modified part of the conducting path. The

treatment of the subjective world along lines calculated investigate the physiology of the nervous system, the

to display that intellectual causative array which character. stronger becomes our belief that for centrifugal discharges

ises science; it merely indicates that this particular applioccur centripetal impulses must be primarily started cation of scientific method is not physiology, but that either in the peripheral sensory surfaces by changes of a something else, still more profound, which is now termed physical or chemical type occurring in the external world, psychophysics. or at some point in the nerve continuum by local chemical But if objective phenomena form the subject matter of or physical changes within the body, especially those due the physiologist, then the legitimate materialism of to the chemical condition of the blood. Having been thus

science must constitute his working hypothesis: and his started they course along definite structural paths, and the

“ well-defined purpose must be to adapt and apply the only direct indications of this passage consist of such methods of physics and chemistry for the analysis of such phenomena as would be produced by the redistribution of phenomena as he can detect in all physiological tissues, concentrated groups of electrolytesma purely physico- including the nervous system. The trend of such a strictly chemical process.

physiological analysis is towards a conception in which the This conception places the propagation of the nervous highest animal appears as an automaton composed of differ, excitatory state as the sole determining factor of nerve

entiated structures exquisitely sensitive to the play of activities, central or peripheral. It derives additional sup

physical and chemical surroundings. The various parts of port from the circumstance that it is in harmony with that the animal body are linked by circulating Avids and ho aspect of these activities which is comprised under the one special structure, the nervous system : in this linking term, inhibition. Any effective regulating system must be of parts the physiologist detects the working of automatic able to bring into play both incentive and restraint-the

chemical mechanisms of great delicacy which once de whip and the reins. The possession by the central nervous veloped, are retained and perfected in proportion as they

efficiently regulate the various bodily activities and com I Gotch and Rurch, Journ. of Physiol., vol. xxiv, 1800, P. 410: Roycott, ordinate them for the welfare of the whole organism. The Inurn. or Physiol., vol. xxiv, 1897, p. 144 ; Buchanan, Journ. of Physiol., vol. xxvii 1901, D.OR &c Gotch and Horsley, Phil. Trans., vol. clxxxii. pp. 267-526. (London,

i Sher ington, Proc. Roy. Soc., vol. Ixxvi B, pp. 269-797. (l*do, 1872)

? See Hovlev, "On the Hypothesis that Animals are Autosti 3 Baglioni, Archiv f. die Ges. Physiol., 19oo, Supplement, pp. 193-242. Evenine : Address. Brit. Assoc , Belfast, 1874. Re-published in “ Collected (Leipzig.)

Essays," vol. i. (Macmillan, 1904.)

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