24 THE MECHANISTIC THEORY OF LIFE 



The manner in which the mechanistic theory 

 endeavours to meet the objections of the 

 vitalists has already been indicated, but will 

 be examined more closely in the second lecture. 

 Meanwhile let us see what are the objections 

 to vitalism. 



' Assuming the vitalistic theory, the simplest 

 observations show us that the action of the 

 vital principle is dependent on physical and 

 chemical conditions of environment, and on 

 the physical and chemical structure of the 

 organism. If, for instance, the temperature 

 is too high or too low, or if the supply of 

 oxygen, or even of some inorganic salt, is cut 

 off, all characteristic signs of life soon cease. 

 The same is the case if the finer structure of 

 the living material has been seriously damaged 

 * by physical or chemical agents. It is thus 

 ' only under certain limiting physical and 

 chemical conditions that the vital principle 

 can manifest itself. Provided, however, that 

 ~ these limiting conditions are present there 

 appears, at first sight, to be a wide field for 

 the manifestation of the influence of the 

 vital principle. If, for instance, a certain 

 minimum of oxygen or of food-material is 



