92 ON THE PLACENTAL STEUCTUKES OF THE TENREC 



the chorion to the after-birth, along" which any matter secreted by 

 the uterine mucous coat can pass. And it is precisely over the 

 part of the chorion which forms one side of this triangular space 

 that these villi spring up, according to BischofF, in the later stages 

 of pregnancy — at a period, that is, in which the non-vascular, 

 non-secreting decidua reflexa is absorbed, and the secretion of the 

 non-placental mucous membrane, whatever it may be, can be 

 brought into relation with, and absorbed by, the foetal vessels. 

 This appears to be a very beautiful instance of natural economy. 

 In the Leporidae, it is true, the chorion is not attached to the 

 centre of the placentulae, and it therefore has not that partial 

 protection from the pressure of the uterine walls for the omphalo- 

 mesenteric circlet of villi which the placentae of the rodents we 

 are speaking of enjoy; but as their decidua reflexa is but a rudi- 

 mentary fringe, whatever is secreted by the uterine walls can at 

 all times come into immediate relation with the omphalo-mesenteric 

 vessels, and be absorbed by, or interchange products with them. 

 In no rodent that I have examined is the non-decidous serotina 

 separable as a distinct and coherent layer from the circular muscular 

 coat ; in all rodents the placental site is on the mesometrial border, 

 and in all also, and not merely in the rabbit 1 , does the chorion 

 receive a vascular supply from the omphalo-mesenteric as well as 

 from the umbilical arteries. In all rodents that I have examined 

 at the time of their birth the omphalo-mesenteric vessels were 

 persistent. In this point they agree with the Carnivora ; and 

 in that of these vessels being supplied to the chorion, the vampire 

 resembles them. 



Simiadae. 



A female pig-tailed monkey (Macacus nemestrinus) having died 

 after giving birth to a foetus, and having had one of its two 

 morbidly adherent placentae removed by artificial means before its 

 death, the maternal vessels were injected with a red, and the foetal 

 with a chrome-yellow injection. One of the two placentae was 

 in its natural position ; and from it a triangular slice was removed 

 for microscopic and other examination. The deeper layers of 

 mucous tissue which are exposed over the site of the placenta, 

 artificially removed in the hope of saving the animal's life, are 



1 Kolliker, 1. c. p. 164. 



