294 



Dr. M. Watson. 



Bat farther, a comparison of the placenta of the racoon with that of 

 the bitch and cat shows that in one important particular Procyon agrees 

 with. Ganis rather than with Felis. As has long been known, the 

 uterine surface of the placenta of the cat, after being detached from 

 the uterus, is covered with a distinct and continuous layer of decidua 

 serotina, whereas, in the bitch, as shown by Professor Rolleston,* this 

 is not the case. In this animal, the deciduous portion of maternal 

 tissue consists simply of the intra-placental processes which are 

 detached along with the placenta, whilst the uterine mucous membrane 

 is not deciduous, but remains adherent to the wall of the womb. 

 Such is also the case in Procyon, and consequently in it, as in the 

 bitch (and apparently also in the fox),f the uterine mucous membrane 

 forms a continuous lining to the wall of the uterus, after detachment 

 of the placenta; whereas, in the cat, according to Turner, + subsequent 

 to the separation of that organ, only the deeper part of the sub- 

 epithelial connective tissue of the uterine mucous membrane remains 

 adherent. Whether, in Procyon, the epithelium of the uterine mucous 

 membrane is normally detached along with the placenta, unfortunately 

 I could not determine. 



Professor Turner has observed that in the mucous membrane of the 

 placental area of the sloths§ and seals. j| the uterine glands appear to 

 undergo a retrograde metamorphosis, and to become of little functional 

 importance during the latter period of pregnancy. The same remark 

 holds good of the uterine mucous membrane of Procyon in which, 

 as already shown, the uterine glands, although well developed, and 

 present in large numbers in the unimpregnated horn, are with difficulty 

 recognisable in the non-placental area of the gravid horn, and then only 

 in a fragmental form, whilst, in the placental area, they have entirely 

 disappeared. It would appear, therefore, that, at least in the Carni- 

 vora, the uterine glands are functionally inactive subsequent to the 

 period when the placenta has been fully developed. 



Whilst, however, the placenta of racoon agrees thus far with that of 

 other Carnivora, it differs materially in respect of the structure of the 

 blood-vessels which constitute by far the larger portion of that organ. 

 As already observed, Professor Turner met with similar vessels in the 

 placenta of Cholcepus. In that animal, however, the placenta is dome 

 or bell-shaped and not annular in character. So far as I can ascertain, 

 ClwlcBjpus and Procyon are the only genera in which these vessels have 

 been hitherto discovered. In every particular, except the elastic 

 nature of their walls, the foetal vessels of Procyon agree with the 



* " Trans. Zool. Soc," v, 1863. 



f Turner, " Lectures on the Comparative Anatomy of the Placenta," p. 85. 

 + Ibid., p. 80. 



§ " Trans. Koy. Soc. Edin.," vol. xxvii, p. 100. 

 || Ibid., xxrii, p. 300. 



