90 WHAT IS LIFE 



new way. Such a machine is quite inconceivable. 

 Yet even the most strenuous supporters of the 

 mechanical school are constrained to admit that 



V 



the living thing constantly varies its method of 

 meeting the various conditions with which it is 

 confronted. " A living being," says M. Le Dantec, 1 

 " is not like an industrial machine manufactured 

 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 ex- 

 aggeration an animal never does twice the same thing 

 in the whole course of its existence" 



The argument in the book from which this 

 quotation has been taken is that the actions of 

 living things are the result of tactisms and that 

 these are due to changes in the chemical composi- 

 tion or reactions of the colloids of which the body 

 is made up. Of what nature, one may fairly ask, 

 are those chemical compounds which never react 

 twice in the same way ? 



Even amongst the smallest and simplest forms 

 1 Op. cit., p. 67. 



