202 BIOLOGICAL ASPECTS OF HUMAN PROBLEMS 



The race would certainly be a great gainer if intel- 

 ligent and deliberate selection for intellectual and 

 moral qualities could be substituted for selection 

 based largely on the attraction of mere beauty, 

 wealth, or social rank. 



In considering the effect of heredity on human 

 offspring an important distinction has to be recog- 

 nized the distinction between true hereditary 

 qualities that are impressed on the germ plasm and 

 various kinds of damage inflicted on the germ plasm 

 by injurious agents, such as poisons or effects aris- 

 ing from impairment in nutrition. It is well known 

 that ordinary acquired characters are not trans- 

 mitted to the offspring. For example, the circum- 

 stance that a father or mother has lost an arm or 

 leg previously to the time of conception has no effect 

 on the offspring ; and, indeed, mutilations generally 

 are without perceptible influence. Similarly, there is 

 no evidence that if a man, by exercises (as rowing), 

 greatly develops his biceps muscles, his child 

 will have large biceps muscles. But while there is 

 thus no specific transmission of such an acquired 

 character, all influences that bring good physical 

 development to the father or mother may bring a 

 greater store of energy to the germ cells by improv- 

 ing their supply of nutriment by way of the blood 

 stream. On the contrary, all conditions that en- 

 feeble the body are liable to diminish the store of 

 energy in the germ cells by decreasing their nutri- 

 ment from the blood stream. It should be clear 



