DEA TH. 249 



possessors from the operation of many of the stimuli 

 of life, and a corresponding degeneration ensues. 



The last phenomenon we have to consider is death. 

 We have already given a hint of its origin in dis- 

 cussing the reproduction of the metazoa. In the 

 reproduction of the metazoa there is a division of 

 the protoplasm of the organism — certain parts di- 

 vided off repeat in each case the cycle of life from 

 the beginning. Another part, however, which has 

 become too highly specialised by the forces acting 

 upon it, cannot return to the original condition, — 

 cannot repeat the cycle of life, — but must continue, 

 without a break, its reactions to its environment. 

 There is an approach to a condition of the continu- 

 ous action of the same forces upon a body. A force 

 acting continuously on any inanimate body composed 

 of a complex molecular or mechanical system, shows 

 two phases of action. First, there is a time when 

 the force is used in producing changes within the 

 body, overcoming resistance and friction, and chang- 

 ing molecular conditions. This time may be com- 

 pared with the period of development of living 

 bodies. It is followed by a time when the force 

 acting reaches an equilibrium with the resistance, — 

 no longer produces internal changes, and in its con- 

 tinued action none of it becomes latent in the body, 

 but escapes in the same quantity as it entered. This 



