SCIENCE. 



427 



lull force. Nor did its strength abate for long after Har- 

 vey's time. The same ingrained tendency of the human 

 mind to suppose that a process is explained when it is 

 ascribed to a power of which nothing is known except 

 that it is the hypothetical agent of the process, gave rise, 

 in the next century, to the animism of Stahl ; and later 

 to the doctrine of a vital principle, that asylum igno- 

 ran/ice of physiologists, which has so easily accounted for 

 everything and explained nothing, down to our own times. 



" Now, the essence of modern, as contrasted with 

 ancient physiological science, appears to me to lie in its 

 antagonism to animistic hypotheses and animistic phrase- 

 ology. It offers physical explanations of vital phenomena, 

 or frankly confesses that it has none to offer. And, so 

 far as I know, the first person who gave expression to 

 this modern view of physiology, who was bold enough to 

 enunciate the proposition that vital phenomena, like all 

 the other phenomena of the physical world, are in ulti- 

 mate analysis, resolvable into matter and motion, was 

 Rene Descartes. The fifty-four years of life of this most 

 original and powerful thinker are widely over-lapped on 

 both sides by the eighty of Harvey, who survived his 

 younger contemporary by seven years, and takes pleasure 

 in acknowledging the French philosopher's appreciation 

 of his great discovery. In fact, Descartes accep'ed the 

 doctrine of the circulation as propounded by ' Herva;us, 

 medecin d'Angleterre,' and gave a full account of it in his 

 first work, the famous ' Discours de la Methode,' which 

 was published in 1637, only nine years after the exercita- 

 tion ' De motu cordis ;' and, though differing from Har- 

 vey in some important points (in which it may be noted, 

 in passing, Descartes was wrong and Harvey right), he 

 always speaks of him with great respect. And so im- 

 portant does the subject seem to Descartes, that he re- 

 turns to it in the ' Traite des Passions,' and in the 

 ' Traite de l'Homme.' 



" It is easy to see that Harvey's work must have had a 

 peculiar significance for the subtle thinker, to whom we 

 owe both the spiritualistic and the materialistic philoso- 

 phies of modern times. It was in the very year of its 

 publication, 1628, that Descartes withdrew into that life 

 of solitary investigation and meditation of which his phil- 

 osophy was the fruit ; and, as the course of his specula- 

 tions led him to establish an absolute distinction of Na- 

 ture between the material and the mental worlds, he was 

 logically compelled to seek for the explanation of the 

 phenomena of the material world within itself, and having 

 allotted the realm of thought to the soul, to see nothing 

 but extension and motion in the rest of Nature. Des- 

 cartes uses ' thought ' as the equivalent of our modern 

 term ' consciousness.' Thought is the function of the 

 soul, and its only function. Our natural heat and all the 

 movements of the body, says he, do not depend on the 

 soul. Death does not take place from any fault of the 

 soul, but only because some of the principal parts of the 

 body become corrupted. The body of a living man differs 

 from that of a dead man in the same way as a watch or 

 other automaton (that is to say, a machine which moves 

 of itself) when it is wound up, and has in itself the physi- 

 cal principal of the movements which the mechanism is 

 adapted to perform, differs from the same watch or other 

 machine when it is broken, and the physical principle of 

 its movements no longer exists. All the actions which 

 are common to us and the lower animals depend only on 

 the conformation of our organs and the course which the 

 animal spirits take in the brain, the nerves, and the mus- 

 cles, in the same way as the movement of a watch is pro- 

 duced by nothing but the force of its spring and the fig- 

 ure of its wheels and other parts. 



" Descartes' treatise on ' Man ' is a sketch of human 

 physiology in which a bold attempt is made to explain all 

 the phenomena of life, except those of consciousness, by 

 physical reasonings. To a mind turned in this direction 

 Harvey's exposition of the heart and vessels as a hydraulic 



mechanism must have been supremely welcome. Des- 

 cartes was not a mere philosophical theorist, but a hard- 

 working dissector and experimenter, and he held the 

 strongest opinion respecting the practical value of the new 

 conception which he was introducing. He speaks of the 

 importance of preserving health, and of the dependence 

 of the mind on the body being so close that perhaps the 

 only way of making men wiser and better than they are is 

 to be sought in medical science. ' It is true,' says he, 

 ' that as medicine is now practised it contains little that is 

 very useful ; but without any desire to depreciate, I am 

 sure that there is no one, even among professional men, 

 who will not declare that all we know is very little as com- 

 pared with that which remains to be known ; and that we 

 might escape an infinity of diseases of the mind, no less 

 than of the body, and even perhaps the weakness of old 

 age, if we had a sufficient knowledge of their causes and 

 of all the remedies with which nature has provided us.' * 

 So strongly impressed was Descartes with this that 

 he resolved to spend the rest of his life in trying to 

 acquire such a knowledge of nature as would lead to the 

 construction of a better medical doctrine.* The anti-Car- 

 tesians found material for cheap ridicule in these aspira- 

 tions of the philosopher ; and it is almost needless to say 

 that, in the thirteen years which elapsed between the pub- 

 lication of the ' Discours ' and the death of Descartes, he 

 did not contribute much to their realization. But for the 

 next century all progress in physiology took place along 

 the lines which Descartes laid down. 



" The greatest physiological and pathological work of 

 the seventeenth century, Borelle's treatise ' De motu ani- 

 malium,' is, to all intents and purposes, a development of 

 Descartes' fundamental conception ; and the same may be 

 said of the physiology and pathology of Boerhaave, whose 

 authority dominated in the medical world in the first half 

 of the eighteenth century. With the origin of modern 

 chemistry and electrical science, in the latter half of the 

 eighteenth century, aids in the analysis of the phenomena 

 of life, of which Descartes could not have dreamed, were 

 offered the physiologist. And the greater part of the 

 gigantic progress which has been made in the present cen- 

 tury is a justification of the provisions of Descartes. For 

 it consists essentially in a more and more complete reso- 

 lution of the grosser organs of the living body into phy- 

 sico-chemical mechanisms. ' I shall try to explain our 

 whole bodily machinery in such a way that it will be no 

 more necessary for us to suppose that the soul produces 

 such movements as are not voluntary than it is to think 

 that there is in a clock a soul which causes it to show tne 

 hours. 't These words of Descartes might be appropri- 

 ately taken as a motto by the author of any modern treat- 

 ise on physiology. 



" But though, as I think, there is no doubt that Des- 

 cartes was the first to propound the fundamental 

 conception of the living body as a physical mechanism, 

 which 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 be- 

 tween the machines with which he was familiar, such as 

 clocks and pieces of hydraulic apparatus and the living 

 machine. In all such machines there is a central source 

 of power, and the parts of the machine are merely pas- 

 sive distributors of that power. The Cartesian 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 doctrine of 

 " natural faculties," nevertheless had the great merit of 

 perceiving that local forces play a great part in physiology. 

 The same truth was recognized by Ghsson, but it was 

 first prominently brought forward in the Hallerian doc- 

 trine of the 'vis insita' of muscles. If muscle can con- 

 tract without nerve, there is an end of the Cartesian me- 



* Discours de la Methode. 6mo. partie. Ed. Cousin. P. 193. 

 t De la Formation du Foetus. 



