204 BIOLOGICAL ASPECTS OF ^HUMAN PROBLEMS 



exerted, since it is true that the criteria of judgment 

 on this point are, as already indicated, by no means 

 simple or convincing. The question of such trans- 

 mission must, therefore, be left open. There is, 

 however, one salient fact of biology that renders a 

 blind and hopeless fatalistic standpoint an unten- 

 able one. Admitting it to be true that the parent 

 cannot improve the hereditary quality of the germ 

 cells which he holds in trust for his line and for the 

 race, it is nevertheless true that the conduct of the 

 parent may detrimentally influence the germ plasm 

 so as to lower the maximal possibilities of good for the 

 offspring. The germ cells are sensitive to poisons, 

 and may be poisoned in a variety of ways by the 

 blood stream of the parent. This is true of both the 

 male and female cells. The excessive use of alcohol, 

 the poisons of syphilis and of malaria, the poisonous 

 action of lead, are all examples of agencies that may 

 greatly harm the germ cells and the beings to which 

 they are destined to contribute. The damaging 

 effect may be so great as to kill the germ plasm. 

 Then there is sterility. Or the effect of the poison 

 may not be so severe as to kill the germ plasm, but 

 may damage it in obscure ways that lead to physical 

 and mental underdevelopment, or to some well- 

 defined disturbances, as epilepsy, or insanity, or a 

 generally unstable nervous system. There are many 

 other poisons that injuriously affect the germ plasm 

 as the chronic poisoning in kidney disease, in 

 gout, and in diabetes, or in tuberculosis. The exact 



