( 617 ) 



amorphous coiHlitioii T have not l)een al)lo to li'aco in sucli spots. 

 Tlie discok:» ration of the tissue may be explained in this way tliat 

 tiie hh)0(l-eorpuscles give otF their haemoi^lobine to the surrounding 

 parts and tiiat tliis is absorbed gradually by the surrounding placenta- 

 tissue. This latter point is the most significant part of the process, 

 for, why should this surrounding tissue, which, unlike the corpuscles, 

 can hardly be regarded as having died off, absorb the altered blood - 

 pigment so uniformly ? That we have here no post-mortem pheno- 

 menon appears clearly on examination of the blood-vessels at the 

 edge of the placenta. As already stated, this is of a more intense 

 yellow hue than that of the spots imder the foetal surface, partly 

 through the more considerable amount of pigment. Now, we find in the 

 tissue of the border of the placenta, several vessels, the lumen of 

 which, in addition to blood-corpuscles, is filled witli pigment. These 

 are foetal vessels. In the vasa umbilicalia I only found some blood, 

 but no pigment. 



The presence of this pigment in the vessels proves, that this yellow 

 hue of the placenta-tissues is a vital reabsorption-process, and not 

 one of post-mortem diffusion. There is another fact in favour of 

 this view : it is my discovering (in the border-zone, where the 

 villi are not very much elongated and the villous epithelium, or 

 chorion ectoderm, is still intact), some distinct pigment-particles in 

 these cells, which had been absorbed from the pigment situated close 

 against this epithelium. 



And on further comparing the structure of the placenta of Plioca 

 with that of fissipede carni^•ores (e. g. the dog), it is found that the 

 spongy layer is entirely missing; all along the thickness of the 

 placenta the same uniform structui-e is maintained. 



The foetal surface of the placenta is covered with a layer of 

 the allantois, coated with a single layer of flat endothelium, as 

 already described. Underneath this, thei'e is a thin layer of fairly 

 firm connective tissue, in Avliich the larger i-amifications of the umbilical 

 vessels are found. 



From this tissue coarse septa of connective tissue find their way 

 into the placenta, which gradually diminish as they run towards 

 the foetal surface, although they usually succeed in reaching it. In 

 these septa the ramifications of the foetal vessels are found. Coarse 

 septa send out finer compartments in every direction. The coarser 

 ones divide the very compact mass of placenta into smaller sections. 



From the maternal side too, some septa of connective tissue filling 

 up the aforesaid grooves on the foetal side of the placenta, enter 

 the latter; I hey are however less voluminous than those coming 



41* 



