196 VITALISM AND SCHOLASTICISM 



as the result of a stimulus, changes have taken 

 place in the organism, say that a muscle has 

 become altered in structure and tired by long 

 use, it has the power, after a time of rest, to 

 return to its former condition, so that on the 

 stimulus being repeated it will be found that 

 the muscle can respond to it as it did on the 

 previous occasion. The machine, on the con- 

 trary, has no power of repairing injuries or wear 

 and tear which may take place in it as the re- 

 sult of its ordinarly use ; it cannot lubricate itself 

 or clean itself or make itself ready for new action. 



And thirdly, no machine can beget a new 

 machine nor has any one succeeded in con- 

 structing anything which, by division, will 

 shape itself into two instruments where but 

 one existed before. It is only and properly 

 so in a living organism that we talk of irrita- 

 bility, of stimuli, of reflex actions, and it is 

 a hopeless task to attempt to explain an 

 organism on mechanical principles. 



In a machine the movements of the rollers, 

 wheels, levers and other parts can be explained 

 on purely mechanical principles, but in the 

 organism the operations of a chemical char- 

 acter, extraordinarily varied as they are, cannot 

 be explained in this way. 



Whilst in the machine the movements of the 

 various parts are firmly united to one another 



