52 



EXPERIMENTAL STUDIES ON FETAL ABSORPTION. 



comes in contact with the maternal tissue of the uterine wall. Goldmann showed 

 that in the mouse this layer of cells plays an important role, similar to that of 

 chorionic epithelium, in the transmission of nutritive material from mother to fetus. 

 The endodermal cells have an enormous capacity for storing colloidal material. 

 They, as well as the chorionic epithelium of the placenta, are responsible for the 

 failure of foreign colloids, injected into the maternal blood-stream, to enter the 

 fetus (figs. 5 and 10) . These same endodermal cells appear to act as a barrier to the 

 passage of colloids in the opposite direction, from fetus to mother, for in the vit ab- 

 stained fetuses the same cells are heavily laden with dye (fig. 11). 



Placenta. — Trypan-blue is absorbed and stored in a few of the endothelial 

 cells lining the capillaries supplying the chorionic villi. These cells are laden with 

 granules of dye and protrude into the lumina of the vessels. 



OBSERVATIONS UPON FETAL CATS. 



The development of the fetal membranes of the cat and other carnivora differs 

 markedly from that observed in rodents, such as the mouse, rat, and guinea-pig. 

 One of the essential differences is that in carnivora the embryo develops upon the 

 surface of the blastodermic vesicle instead of within it, and consequently the germ 

 layers do not undergo inversion. In the cat fetus we find as the outermost fetal 

 covering the amniogenic chorion. A well-developed allantois separates chorion and 



Ammog'enic 

 Chorion 



Allantoic 

 Chorion 



Outer 



Inner 



Layer- 



of 

 AllanVois 



Chorionic 

 Villi 



Text-figure No. 1. — Diagrammatic representation of the fetal 

 membranes of the dog. (After Bonnet.) 



amnion. The yolk-sac is entirely closed and becomes reduced in size as pregnancy 

 advances. The placenta surrounds the fetus as a broad, circular band, hence called 

 placenta zonaria. A diagram (text-figure 1) borrowed from Bonnet (1907) makes 

 these relationships clear. Trypan-blue was injected into the amniotic cavities of a 

 number of cat fetuses during the latter part of pregnancy. Vital staining of the fe- 

 tuses always occurred. Two litters of kittens, living and vitally stained, were born 5 

 and 8 days respectively after a single injection of trypan-blue into the amniotic sacs. 



