498 



THE AM E LUC AN NATURALIST 



[Vol. XLII 



the placenta and affecting the young in utrro. It also appeared 

 to multiply rapidly in the fetal circulation. 



In cases of congenital syphilis, Treponema pallidum has been 

 shown to be present in small numbers in the blood taken from 

 placenta and cord and undoubtedly has the power to pass through 

 the placental tissue from maternal to fetal circulation. While a 

 final decision can not be reached at present, the weight of evi- 

 dence favors the view that Treponema is an animal rather than a 

 bacterium. In some closely related forms the conditions have 

 l)oen more definitely established. Thus in Spirochacta duttoni, 

 the cause of African relapsing fever, Breinl and Kinghorn, 4 

 in four rats and one guinea-pig, demonstrated the passage of the 

 spirochete through the placenta into the fetus. The parasites 

 were found in the placenta in approximately the same numbers 

 as in the heart blood of the mother, yet in very meager numbers 

 in fetal blood. There was no tendency to abort, yet a large per- 

 centage of young died shortly after birth. The spirochetes from 

 fetal heart blood showed themselves virulent on inoculation. 



These and similar cases among animal parasites are not sur- 

 prising. They differ from the accidental contamination of the 

 young at birth in the case of bacterial diseases only in that the 

 infecting agent is capable of migration through solid tissue and 

 thus passes barriers in the placenta which constitute obstacles to 

 the passage not only of bacteria but also of some other animal 

 organisms, like the plasmodium already noted, which do not 



ductive organs or function. 



Certain cases are known, however, in which the conditions are 

 radically different. One of the first of these was the demonstra- 



