ii8 The Third and Fourth Generation 



also directly afifect the germ plasm and produce 

 heritable results. 



There is one set of diseases which, while they 

 are not heritable in the sense that they are 

 transmitted through the germ plasm, are yet 

 directly passed from the parent to the offspring. 

 These are some of the venereal diseases, such 

 as syphilis and gonorrhea. They are no more 

 heritable than smallpox or scarlet fever, but 

 since they are diseases of the sex organs, and 

 the child in the process of being born must come 

 in contact with these sex organs, the child is 

 practically certain to catch the disease from its 

 parent. They are exceedingly persistent and 

 readily infectious. While they are commonly 

 passed from individual to individual by the 

 intercourse of the sexes, a perfectly innocent 

 person may get the contagion by using an 

 unclean toilet or merely by personal contact, 

 touching or kissing an individual who is 

 seriously affected with the disease. Gonorrhea 

 is responsible for a very large percentage 

 (probably 80 per cent) of the blindness of 

 infants and for a large percentage of the opera- 



