August II, 1881] 



NATURE 



345 



" I .'hall trv to explain our whole bodily machinery in such a 

 way, that it will be no more necessary for us 10 suppose that the 

 soul produL-es such movements as are not voluntary, ihan it is to 

 think that there is in a cluck a soul which causes it to show the 

 hours."' Thesi; wurds of Descartes might be appropriately taken 

 as a motto by the author of any modern treatise on physiology. 



But thou.;h, as I think, there is no douljt that Descartes was 

 the fir-t to propound the fundamental conception of the living 

 body as a physical mechanism, wliich is the distinctive feature of 

 modern, as contrasted with ancient physiology, he was misled by 

 the natural temptation to carry out, in all its details, a parallel 

 between the machine- with which he was familiar, such as clocUs 

 and pieces tif hydr^iulic app:iratus, and the living machine. In 

 all such machines there is a central source of power, and the parts 

 of the machine a'e merely passive distributors of that power. 

 The Cariesian school conceived of the living body as a machine 

 of this kind ; and herein they might have learned from Galen, 

 who, whatever ill use he may have made of the doctrme of 

 "natural faculties," nevertheless had the ijreat merit of perceiving 

 thai local forces play a great part in physiology. 



The same truth was recognised by Gbsson, but it was first 

 prominentlv brought forward in the Hallerian doctrine of the 

 "vis insita " of mu cles. If muscle can contract without nerve, 

 there is an end of the Cartesian mechanical explanatijn of its 

 contraction by the influx of animal spirits. 



The di-coveries of Trembley tended in the sa ue direction. In 

 the freshwater Hydra, no trace was to be found of that compli- 

 cated machinery upon which the performance of the functions in 

 the higher animals was supposed to depend. And yet the hydra 

 moved, fed, grew, multi|ilied, and its fragments exhibited all the 

 povers of the whole. And, finally, the work of Caspar F. 

 Wolff, - by demonstrating the fact that the growth and develop- 

 ment of both plants and animals take place antecedently to the 

 existence of their grosser organs, and are, in fact, the causes and 

 not the consequences of orgaoisation (as then understood), 

 sa|)ped the f lundations of the Cartesian physiology as a complete 

 expression of vital phenomena. 



For Wolff, the physical basis of life is a fluid, possessed of a 

 "vis es-entialis" and a "solidtscibilitas," in virtue of which it 

 gives rise to organisati(m ; and, as he points out, this conclusion 

 strikes at the root of the wh')le iatro-mechanical .system. 



In thi- country, the great authority of folin Hunter exerted a 

 similar influence ; though ii must be admitted that the two sibylline 

 uttera'ices which are the outcome of Hunger's struggles to ciefine 

 hisconceptionsareofteusu ce|itibleof morethan one interpretation. 

 Nevertheless, on some points. Hunter is clear enough. For 

 example, he is of opini )n that "Spirit is only a property of 

 matter" ("Introduction to Natural History," p. 6), he is 

 prepared to ren >unce animism [I c. i?. 8), and his conception of 

 life is so complerely physical tint he thinks of it as something 

 which can exi-t in a state of combination in the food. " The 

 aliment we take in has in it, in a fixed state, the rex\ life ; and 

 this does not become active until it has got into the lungs ; for 

 there it is freed from its prison " (" Obseirvations 0:1 Physiology," 

 p. 113). He also thinks that "It is mo.e in aecorl with the 

 general principles of the animal machine to suppose that none of 

 its effects are produced from any mechanical principle whatever ; 

 and that every effect is produced from an action in the part ; 

 which action is |jroduced by a stimulus upon the part which acts, 

 or uprjn so ne other part with which this part sympathises so as 

 to tal^e up the whole action " (/,r. p. 1 52). 



And Hunter is as clear as WoJff, with whose woik he was 

 probably unicquainted, that "whatever life is, it most certainly 

 does not depend upon structure or organisation" {I.e. p. 114). 



Of course it is imp issible that Hunter could have intended to 

 deny the existence of purely mechanical operations in the animal 

 body. But while, with Borelli and B jerhaave, he looked upon 

 absorption, nutrition, and secretion, as operatiims effected by 

 means of the small vessels ; he differed from the mechanical phy- 

 siologists, who regarded these 0|)erations as the result of the 

 mechanical propertie> of the small vessels, such as the size, form, 

 and disposition of their canals and aperiures. Hunter, on the 

 contrary, considers them to be the effejt of properties of these 

 ves els which are not mechanical but vi'al. *' The vessels," says 

 he, " have more of the polypus in them than any other part of the 

 body," and he talks of the "living and sensitive principles of the 

 arteries, " and even ofthe"di- positions or fee I ings of th :; arteries." 

 " When the blood is gooi and genuine the sensations of the 



arteries, or the dispositions for sensation, are agreeable. ... It 

 is then they dispose of the blood to the best advantage, increasing 

 the growth of the whole, supjilying any losses, keeping up a due 

 succession, &c." (/. c. p. 133 ) 



If we follow Hunter's conceptions to their logical issue, the 

 life of one of the higher aniaials is essentially the sum of the 

 lives of all the vessels, each of which is a soit of physiological 

 unit, answering to a polype ; and, as health is the result of the 

 n irmal "action of the vessels," s) is disease an effect of their 

 abnormal action. Hunter thus stands in thought, as in time, 

 midway between Borelli, on the one hand, and Bichat on the 

 other. 



The acute fjunder of g<ineral .anatomy, in fact, outdoes Hunter 

 in his desire to exclude physical reasonings from the realm of 

 life Except in the interpretation of the action of the sense 

 organs, he will not allow physics to have anything to do with 

 physiol ,gy. 



" To apply the physical sciences to physiology is to explain the 

 phen )mena of living bodies by the laws of inert bodies. Now 

 this is a false principle, hence all its consequences are marked 

 with the same stamp. Let us leave to chemistry its affinity, to 

 physics, itsclasticily and its gravity. Let us invoke for physiology 

 only sensibility and contractility." ' 



Of all the unfortunate aicta of men of eminent ability this 

 seems one of the most unhappy, when we think of what the 

 application of the methods and the data of 1 hysics and chemistry 

 has done towards bringing physiology into its present state. It 

 is not too much to say that one half of a modern text-book of 

 physiology consists of applied physic- and chemistry ; and that 

 it is exactly in the ex|>loration of the phenomena of sensibility and 

 contractility that physics and chemistry have exerted the most 

 potent mduence. 



Nevertheless, Bichat rendered a solid service to phy-iological 

 progress by insisting upon the fact that what we call life, in one 

 of the higher animals, is not an indivi-ible unitary arcbseus 

 dominating, from its central seat, the parts of the organism, but 

 a compound result of the synthesis of the separate lives of those 

 parts. 



"All animals," says he, "are assemblages of different organs, 

 each of which performs its function and concurs, after its fashion, 

 in the preservati m of the whole. They are so many special 

 machines in the gener .1 machine which constitutes the individual. 

 But each of these special machines is itself compounded of many 

 tissues of very different natures, which in truth c )nslitute the 

 elements of those organs." (i.e. Ixxix.) " The conception of a 

 proper vitality is applicable only to these simple tis u=s, and not 

 to the organs themselves." (I.e. Ixxxiv.) 



And Bichat proceeds to make the obvious application of this 

 doctrine of synthetic life, if I may so call it, to jiathology. 

 Since di eaes are only altcratims of vital properties, and the 

 properties of each tissue are distinct from those of the rest, it is 

 evident that the diseases of each tissue mu>t be different from 

 those of the re~t. Therefore, i i any organ composed of different 

 tissues, one may be diseased and the oher remain healthy ; and 

 this is what happens in most cases. (I.e. Ixxxv.) 



In a spirit of true prophecy, Bichat says, "we have arrived 

 at an epjch, in which pathological anatomy should start afresh." 

 For as the analysis of the organs had led him to the tissues, as 

 the physi ilogical units of the organism ; so, in a succeeding 

 generation, the analysis of the ti-saes led to the cell as the 

 physiological element of the tissues. The contemporaneous 

 study of development brought out the same result, and the 

 zoologists and bota lists explormg the simplest and the lowest 

 forms of animated beings confirmed the great induction of the 

 c°ll theory. Thus the apparently opposed views, which have 

 been battling with one another ever since the middle of the 

 last century, have proved to be each half the truth. 



The proposition of Descartes that the bidy of a living man 

 is a machine, the actions of which are explicable by the known 

 laws of matter and motion, is unque-.tioi,ably largely true. But 

 it is also true, that the living body is a syntheis of innumerable 

 phy i ilogical elements, each of which may nearly be described, 

 in Wolff 's words, as a fluid pwsessel of a " vis essentialis," and 

 a " s rlidescibilitas " ; or, in modern phrase, as protoplasm 

 susccp'ible of .structural metamorphosis and functional meta- 

 b .lism : and that the only machinery, in the precise sense in 

 which the Cartesian school understood mechanism, is, that 

 which co-ordinates and regulates these physiological units into 

 an organic whole. 



' "Anatomie generale," i. p. liv. 



