EXPERIMENTAL PROOF. 25 



the placental circulation must, therefore, be recognized as a condi- 

 tion which favors the transmission of microorganisms from mother 

 to fetus. 



All of the foregoing observations and experiments furnish sub- 

 stantial proof that in some infectious diseases heredity is traceable to 

 direct transmission of the specific microbes floating in the circula- 

 tion of the mother to the foetus, through the thin wall which sepa- 

 rates the maternal from the foetal blood. It is no more difficult to 

 explain the migration of microbes through such a thin septum 

 than their transportation from one tissue to another, and from 

 organ to organ in other parts of the body, more especially as the 

 anatomical conditions for mural implantation in the placental 

 vessels are most favorable for such an occurrence. 



