8oo THE POPULAR SCIENCE MONTHLY. 



knew less physiology than is now to be learned from the most element- 

 ary text-book ; and, beyond a few broad facts, regarded what they 

 did know as of extremely little practical importance. Nor am I dis- 

 posed to blame them for this conclusion ; physiology must be useless, 

 or worse than useless, to pathology, so long as its fundamental concep- 

 tions are erroneous. 



Harvey is often said to be the founder of modern physiology ; and 

 there can be no question that the elucidations of the function of the 

 heart, of the nature of the pulse, and of the course of the blood, put 

 forth in the ever-memorable little essay " De motu cordis," directly 

 worked a revolution in men's views of the nature and of the concate- 

 nation of some of the most important physiological processes among 

 the higher animals ; while, indirectly, their influence was j^erhaps even 

 more remarkable. 



But, though Harvey made this signal and perennially important 

 contribution to the physiology of the moderns, his general concej^tion 

 of vital processes was essentially identical with that of the ancients ; 

 and, in the " Exercitationes de generatione," and notably in the singu- 

 lar chapter " De calido innato," he shows himself a true son of Galen 

 and of Aristotle. 



For Harvey, the blood possesses powers superior to those of the 

 elements ; it is the seat of a soul which is not only vegetative but also 

 sensitive and motor. The blood maintains and fashions all parts of 

 the body, '"'' idque simima cum promdentia et intellectu infinem certmn 

 age7is, quasi ratiocinio quodam uteretur.'^'' 



Here is the doctrine of the " pneuma," the product of the philo- 

 sophical mold into which the animism of primitive men ran in Greece, 

 in full force. Nor did its strength abate for long after Harvey's time. 

 The same ingrained tendency of the human mind to suppose that a 

 process is explained Avhen it is ascribed to a power of which nothing is 

 known excej^t 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 ignorantise " 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 physiologi- 

 cal science, appears to me to lie in its antagonism to animistic hypoth- 

 eses and animistic phraseology. 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 ultimate analysis, resolvable into matter and motion, was Reno 

 Descartes. 



The fifty-four years of life of this most original and powerful think- 

 er are widely overlapped, on both sides, by the eighty of Harvey, who 



