On the Female Organs and Placentation of the Racoon. 293 



fied in the caso of the bitch, cat, fox, and seal. The interlocking; 

 of the intra- placental processes of maternal mucous membrane 

 with the foetal chorionic villi, and the separation of both from the 

 uterine wall, have been already described ; and although the processes 

 of maternal tissue could without difficulty be withdrawn from the 

 interstices of the chorionic villi, it must be borne in mind that, at 

 the time of separation of the placenta, the full period of gestation had 

 not been completed, and that, in all probability, had such been the case 

 the union between the foetal and maternal portions of the placenta 

 would have been more intimate than in the specimen examined. 

 Although, owing to the absence of injection, the precise form of the 

 chorionic villi and the mode of interlocking of these with the 

 maternal processes could not be ascertained, there seems little reason 

 to doubt that their arrangement presented a close resemblance to 

 that described by Professor Turner in the placenta of the bitch, cat, 

 and seal. The structure of the maternal portion of the placenta of 

 Procyon, moreover, agrees in all respects with that of the animals just 

 named, consisting as it does of processes of the mucous membrane of 

 the uterus which are richly supplied with capillaries presenting the 

 same structure as those of the uterine mucous membrane itself. A 

 farther resemblance between the maternal processes of the placenta of 

 Procyon and those of the other mammals mentioned is to be found in 

 the presence, in all, of a well-defined layer of columnar epithelial cells 

 investing these processes. 



"With regard to the appearance presented by the uterine surface of 

 the placenta, Procyon agrees rather with Ganis than with Felis. The 

 very regular arrangement of the uterine extremities of the foetal villi, 

 surrounded as they are by the circum-papillate ridges of maternal 

 tissue, is certainly peculiar to the racoon. At the same time, an examina- 

 tion of the uterine surface of the placenta of the bitch, at nearly full time, 

 convinced me that the difference in this respect between the placenta 

 of Procyon and that of Ganis is one of degree rather than of kind. In 

 the latter, although the arrangement of these two constituents on the 

 uterine surface of the placenta is by no means so regular as that met 

 with in the racoon, yet indications of it were plainly observable. In 

 the bitch, as observed by Turner,* and this observation I can confirm, 

 the chorionic villi reach the uterine surface of the placenta much as 

 in Procyon. Surrounding them are numerous ridges of maternal 

 tissue which, although by no means presenting the regular honey- 

 comb appearance met with in the racoon, nevertheless, at places, closely 

 resemble it. In the bitch, these ridges for the most part enclose 

 irregular polygonal spaces, in the centre of each of which lies the 

 uterine extremity of a foetal villus, whereas in Procyon these spaces 

 present a regular honeycomb appearance. 



* " Lectures on the Comparative Anatomy of the Placenta," p. 82. 



