So SEX AND HEREDITY 



This comparative independence, on the part of the young 

 individual, of the peculiarities of the mother, holds under 

 normal conditions. If, however, conditions become 

 abnormal through disease, in particular if the blood- 

 stream of the mother, upon which the welfare of the young 

 individual is completely dependent, becomes abnormal, 

 then there are apt to come about effects upon the health 

 of the young individual which may be disastrous. 

 Poisonous substances in the blood of the mother diffuse 

 into the blood of the embryo and poison it. And various 

 disease-producing microbes have the power of burrowing 

 their way through the thin membrane separating the 

 blood streams of mother and offspring, and thus infecting 

 with the disease the new individual. 



