TRANSMISSION OF INDUCED EYE-DEFECTS 199 
case of two-sexed twins, but that they are there neutralized by 
appropriate antibodies generated in the female fetus, and that 
it is only when the latter is overwhelmed by blood from the male 
through direct continuity of the blood-vessels that the antibodies 
are insufficient to accomplish neutralization. The condition 
known to exist in the blood of pregnant mothers for neutralizing, 
or better perhaps digesting, any placental fragments which may 
escape into the maternal blood-stream renders this hypothesis 
less far fetched than at first sight it might appear to be. 
However this may be, the situation as described by Lillie has 
‘suggested to the authors the necessity of knowing more about the 
manner in which such substances as antibodies get through the 
placenta from mother to young. The junior author is already 
engaged in researches looking toward a solution of this problem. 
Whatever the means, it is obvious that, in general, antibodies 
can penetrate the placenta, since it is well known that induced 
immunity to various forms of bacterial infection are transmitted 
through the placenta to the uterine young. Also it has been 
‘shown that such a foreign substance as madder when fed to preg- 
nant mothers will pass through the placenta and color the bones 
-of the fetal young. It is well established, moreover, that certain 
pathogenic agents may traverse the placenta and produce ante- 
natal infections. 
In our experiments, that all the young were not invaded, or 
that they were unequally invaded, or that being invaded some 
were more resistant than others to the influence of the antibodies, 
is evident from the fact that a very substantial majority of the 
total number of young obtained showed no specific effect of the 
treatments. It is not impossible that in the struggles of the 
mothers, slight breaking down of the walls of the placental blood- 
vessels occurred in some cases, permitting some direct flow of the 
maternal blood into the fetus. And it may be that only such 
fetuses got a sufficient amount of the lens antibodies to have their 
own lenses affected. But whatever the means, the important 
fact is that penetration was accomplished in some way, with the 
result that defective-eyed offspring were occasionally produced. 
