CHAPTER VI. 



DISEASE AND IMMUNITY. 



THE verb "to acquire" means to obtain by 

 effort, exertion, exercise, or performance 



of work of some kind. The verb "to educate" 

 means *'to exercise the mental faculties, as 

 by instruction, training and discipline, in 

 such a way as to develop and render efficient 

 the natural powers." It also means to exer- 

 cise physical powers, as we have such a thing as 

 ^'physical education." And "education" means 

 the "systematic development and cultivation of 

 the mind and other natural powers." 



From the biological standpoint, an education 

 consists of the development of powers by exer- 

 cising them, and not the things learned. This is 

 plain enough in physical education, but is gen- 

 erally confused in speaking of mental education 

 because of the common use of that term "edu- 

 cation" in another sense. The biological educa- 

 tion is the thing acquired, and the only "acquired 

 character" which has any right to that term is 



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