THE BIOLOGICAL SCIENCES AND MEDICINE. 347 



" 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 the hours." * These 

 words of Descartes might be appropriately taken as a 

 motto by the author of any modern treatise on physi- 

 ology. 



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

 cartes was the first to propound the fundamental concep- 

 tion 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 tempta- 

 tion to carry out, in all its details, a parallel between 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 passive distrib- 

 utors 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 facul- 

 ties," nevertheless had the great merit of perceiving that 

 local forces play a great part in physiology. 



The same truth was recognised by Glisson, but it 



was first prominently brought forward in the Hallerian 



doctrine of the " vis insita" of muscles. If muscle can 



contract without nerve, there is an end of the Cartesian 



* " DC la Formation du Frctus." 



