88 DEVELOPMENT AND HEREDITY. 



a very brief time. In fact, were it not for the ability 

 we possess to make our mental and corporeal actions 

 habitual and more rapid of execution, life would be 

 too short for us to aspire to more than its bare 

 necessities. 



We can observe this principle acting in the growth 

 of habits among animals, especially our domestic 

 animals, with which we may be familiarly acquainted. 

 A young bird's first attempts at flight are very im- 

 perfect, but after repeating the action a number of 

 times, perfect power of flight is attained. We find 

 the same awkwardness and inability generally where 

 we see young animals first attempting to co-ordinate 

 their muscular efforts for a definite purpose. The 

 same thing is evident where older animals are placed 

 in new conditions of life, where they are required to 

 attempt entirely new movements. The structure of 

 the nervous system gives evidence that the same 

 state of affairs prevails wherever we find a distinct 

 nervous system ; and the fact that all protoplasm par- 

 takes somewhat of the nature of nervous tissue, in- 

 dicates that, throughout the whole realm of life, the 

 performance of an action tends to become more 

 easily and quickly executed by frequent repetition. 



The difference in the effort with which an action 

 is performed for the first time, and again after much 

 practice, has its correlative in a difference of nervous 



