An Introduction to a Biology 



entrance to the nerves supplying those muscles 

 which were required to be set in motion were flung 

 open, the animal spirits rushed out along the nerves 

 and set the muscles in appropriate action. The 

 essence of this explanation of the performances of 

 the human body is that the body is regarded as a 

 machine. The manner of its action is the result 

 of its structure. It is a theory of the living thing 

 which could not but be immediately intelligible. 

 When the human mind invents or encounters the 

 mechanistic theory of the organism, it is confronted 

 with an apparition which it at once recognises as 

 the darling of its adolescence and the symbol of 

 its DOwer — a machine. No wonder it welcomed the 

 theory with open arms. 



§ 2 



If we look a little closer at the theorv we shall 

 see that it is a materialistic one too. As in the case 

 of the machine all action is the result of the form 

 of the solids of which it is made and of the motive 

 force acting upon its different parts, so in the case 

 of the body, according to this theory, all action, 

 however complicated, is the result of the form of 

 the matter of which the body is made — i.e. of the 

 gross structure of the muscles and limbs and the 

 delicate structure of the nerves, and of the inter- 

 action of the chemical juices which it contains. It 

 is a materialistic conception of the living thing 

 because it means the belief, held by the great majority 

 of biologists at the present day, that all the mani- 

 festations of life are capable of being expressed in 

 terms of matter. 



8S 



