CHAPTER XII 



ARTIFICIAL FUNCTIONS AND FUNCTIONS RATIONALLY 



DEFINED 



WHEN we wish a complete anatomical description of the 

 body of a living being, we can separate it into parts in any 

 number of ways. Just so, there is no reason why we should 

 limit the number of methods by which we analyse the vital 

 activity of the same being. 



A living being is not like an industrial machine manufac- 

 tured with the design of accomplishing a certain kind of 

 work and able to do no other. A locomotive can exercise 

 only the locomotive's function. On the contrary, a dog, a 

 duck, a serpent, are able to manifest in a thousand different 

 ways according to circumstances their specific activity as dog 

 or duck or serpent. Now, circumstances so vary around 

 any given animal and the animal itself changes so quickly 

 that we may say without exaggeration an animal never does 

 twice the same thing in the whole course of its existence. 



Physiologists, however, when comparing the animal to 

 an industrial machine, are accustomed to describe its 

 activity by a decomposition into a certain number of 

 functions which, from the descriptive point of view, are 

 simpler than the total activity of the individual. Just so, 

 in a locomotive we deduce from the backward and forward 

 movements of the piston under the influence of steam pres- 

 sure the transformation of the movement to and fro into a 

 movement of rotation by the play of connecting rods and 



