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Dr. M. Watson. 



indeed of that of any other carnivorous mammal whose placenta 

 has been hitherto described. To the naked eye this surface presented 

 merely a flocculent appearance, but when examined with the aid of a 

 simple lens, or, still better, with the lower powers of the compound 

 microscope (Ross, oc. A, object. 3-incIO, this flocculent appearance 

 resolved itself into a vast number of clearly- denned papillae, which 

 covered the entire uterine surface of the organ. The appearance 

 presented under the microscope is faithfully reproduced in fig. 9. 

 I have said that the papillae covered the entire surface of the placenta ; 

 but, along each border of the organ, there was a narrow band, slightly 

 raised above the level of the surface, where the papillae in question at 

 first sight appeared to be absent. Further examination, however, 

 proved that the papillae were present here as elsewhere, but that their 

 presence was concealed by a superjacent layer of delicate tissue, which 

 proved to be of the same structure as the uterine mucous membrane. 

 This layer must therefore be regarded as representing the decidua 

 reflexa. The papillae, under the microscope, presented an appearance 

 closely resembling that of the villi of the small intestine after a suc- 

 cessful injection with opaque material, but were of considerably larger 

 size. The papillae were mostly club-shaped, the apex of each being of 

 greater diameter than the base. Their summits were for the most 

 part uniformly rounded, but here and there a papilla could be dis- 

 tinguished which presented a central depression on its free extremity. 

 The separate papillae were uniformly simple, and in no one instance 

 did I observe secondary papillae growing out from a primary stalk. I 

 have observed that the separate papillae resembled the intestinal villi, 

 but the surface of the placenta, as a whole, presented a widely different 

 appearance from that of the intestinal mucous membrane. This was 

 due to the fact that each papilla was surrounded by a wall of placental 

 substance, which, as it were, enclosed a space, in the centre of which 

 the papilla was situated, and was thereby completely isolated from its 

 neighbours. These walls were quite continuous all over the surface 

 of the placenta. They were not so high as the papillae which they 

 surrounded ; and, consequently, when the placental surface was viewed 

 obliquely, the walls were hidden at places by the papillae, and appeared 

 to be absent. More thorough examination, however, disclosed their 

 presence over the entire surface of the placenta. The spaces bounded 

 by these walls varied in form. In some places they were square, at 

 others five or six-sided, whilst occasionally they were circular. Look- 

 ing at the placental surface as a whole, its appearance was not unlike that 

 of a honeycomb filled with grubs, the walls corresponding to the 

 partitions between the cells, whilst the papillae very fairly represented 

 the contained grubs. $ 

 Towards the margins of the placenta the arrangement just described 

 undergoes some alteration. In the neighbourhood of the band of 



