CHAPTER VIII. 



THE INHERITED IMPULSE OF DEVELOPMENT, OR TEN- 

 DENCY OF GROWTH. 



We have seen that the process of development "of 

 living things was somewhat as follows. The first 

 living matter was subjected to a variety of constant 

 and intermittent forces, and frequent action of com- 

 bination of forces. These caused mechanical reac- 

 tions. Repetition made these reactions more rapid 

 and easy, and association combined them into reflex 

 series of co-ordinated actions. For the most part, 

 these forces acted on the living things in monoto- 

 nous rounds of repetition, which would have admitted 

 of no change in the individual were it not for two 

 peculiarities of living matter. First, the process of 

 assimilation caused an increase in bulk ; and second, 

 the constant repetition of reactions caused by asso- 

 ciation an increase in the complexity of structure 

 of the paths through which the forces expended 

 themselves in the organism. The repetition and 

 association developed the nervous elements into 



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