94 EXPERIMENTAL STUDIES ON FETAL ABSORPTION. 



themselves, together with the vessels supplying them, appear to degenerate to a 

 great extent. It is interesting to note that this same area is conspicuously blue 

 when the vital dye is injected into the fetal instead of into the maternal blood- 

 stream (figs. 4, 5). 



The behavior of the surface of the placenta, just beneath the vitelline mem- 

 brane, is also noteworthy. The proliferation of the epithelium of the ectoplacental 

 endoderm has already been described and need not be referred to further. Very 

 early in the development of the placenta a layer of fetal syncytium comes to lie 

 directly beneath the membrane. The periphery of this syncytium, however, very 

 soon undergoes a change. It shapes itself into two or three layers of ectodermal 

 cells with large round nuclei surrounded by a wide zone of vacuolated cytoplasm. 

 Duval called attention to these cells on the surface of the placenta of the guinea-pig 

 and referred to them as giant cells. In a section through the border of the placenta, 

 at about the middle of pregnancy, one sees the vitelline membrane beneath which 

 are layers of these giant cells, beneath which in turn is a layer of border syncytium 

 containing large lacunse, and finally the placental labyrinth (fig. 6) . In an animal 

 which has been stained with trypan blue the ectoplasm of the giant cells is filled 

 with fine granules of the dye (fig. 6) . As the end of gestation approaches, these cells 

 become shrunken and in part disintegrate and disappear. 



In the decidua serotina groups of free macrophages, containing varying 

 amounts of trypan blue in their cytoplasm, were encountered. Many of these wan- 

 dering cells appeared to be undergoing degeneration. They were similar to those 

 described by Goldmann in the mouse and rat, which were thought by him to be 

 important in the transfer of nutrient material, such as glycogen, from the tissues 

 and vessels of the decidua to the fetal ectoderm. In the myometrium and serosa, 

 in the neighborhood of the placental attachment, hundreds of similarly stained 

 cells were observed. Goldmann believed that in the mouse and rat many of these 

 are derivatives of the serous cells covering the peritoneal surface of the uterus. 

 This may also be the case in the guinea-pig, for the peritoneal cells were con- 

 spicuously loaded with the dye. 



One further aspect of the behavior of trypan blue is worthy of description. 

 In several of the guinea-pigs used in these experiments large injections of trypan 

 blue were administered, resulting in mild inflammatory changes in the placenta, to 

 judge from a poor staining reaction on the part of the syncytium and the presence 

 of numerous polymorphonuclear leucocytes in the sinusoids. It was observed that 

 the polymorphonuclear leucocytes in the maternal blood-spaces contained numer- 

 ous tiny granules of trypan blue within their cytoplasm (fig. 7) . It has been the 

 general belief that none of the elements of the circulating blood normally stain with 

 vital dyes. Downey (1917), however, has attempted to show that the polymorpho- 

 nuclear leucocyte is capable of ingesting vital dye under certain conditions. In 

 the circulating blood conditions are unfavorable, he claims, for phagocytosis of any 

 kind to occur, and he bases his argument on the failure of the polymorphonuclear 

 leucocytes, while moving rapidly, to take up bacteria, vital dye, or any other par- 

 ticulate matter. Downey has shown experimentally that in the areas where the 



