96 EXPERIMENTAL STUDIES ON FETAL ABSORPTION. 



SUMMARY. 



1. Trypan blue, injected into the pregnant guinea-pig, stains the placenta and 

 the vitelline membrane but does not enter the amniotic fluid or the fetus, except 

 in traces. 



2. A zone of the vitelline membrane covered by villi absorbs the dye very 

 rapidly and in large amount, and may well be termed an attraction center for the 

 dye. The portion of the vitelline membrane covering the placenta, theectopla- 

 cental endoderm, fails to stain vitally. 



3. Trypan blue is absorbed and stored to a slight extent by the ectoderm cover- 

 ing the chorionic villi of the placental labyrinth. It is not taken up at all by the 

 interlobular syncytium or by that part of the ectoderm, composed of giant cells and 

 syncytium, which occupies the central zone (Umlagerungszone) . 



4. The dye appears in the form of fine granules in the layer of giant cells 

 described by Duval, situated beneath the ectoplacental endoderm. 



5. It is also taken up by a host of free macrophages which are found throughout 

 the decidua serotina and the uterine wall. 



6. Carbon particles injected into the maternal blood-stream are not phago- 

 cytosed by any cells of the placenta or fetal membranes. 



