78 ON THE PLACENTAL STRUCTURES OF THE TENREC 



outer margin that it is attached along the line of demarcation be- 

 tween the outer and inner regions of each utero-placental area. 

 In other words, the utero-placental mucous membrane seems to 

 split at this line into two laminae, between which a watch-shaped 

 cavity is included, and each of which is sieve-like centrally from 

 vascular perforations. 



The placenta is thinnest at its centre ; at its periphery the 

 chorion is prolonged upwards in the shape of a circular rim of a 

 depth of a quarter of an inch. The umbilical vessels are very 

 plainly seen to be prolonged into ramifications along this rim, and 

 in it. The rim itself, or upgrowth, is continuous with the parapet, 

 or down growth, of the uterine mucous membrane — an arrangement 

 which, so far as I have been able to find, is unique. 



The umbilical cords of these foetuses are long : the foetuses 

 being about an inch and a half long, the cord is in some instances 

 of equal length with them ; and the cavity of the amnios is large — 

 sufficiently capacious, indeed, to admit of the introduction of a 

 second foetus. Resembling the human foetus more or less in these 

 two points, the foetal membranes of the tenrec resemble those of 

 the ruminants in the possession of numerous corpuscles studding 

 the interior surface of the amnios. These corpuscles are in some cases 

 attached to the inner surface of the amnios, but in most cases they 

 have fallen away from it, in some cases they are filiform or even club- 

 shaped, in most they are boat-shaped, or rather of the shape of a 

 single valve of an ordinary bi-valve, and attached by the concave 

 side to the amnios, whilst projecting with a smooth convex one into 

 its cavity. And as to the naked eye, so under the miscroscope they 

 resemble les plaques de F amnios chez les ruminants, as described by 

 Professor Claude Bernard l . The longer of these corpuscles were 

 as much as two millimetres long by one broad— much the same 

 size in fact as the similarly-placed corpuscles of the elephant 

 described by Professor Owen 2 : many, however, were of smaller 

 dimensions. 



I could not discover any traces of yelk-sac, nor of allantois, nor 

 of any membrane exterior to the amnios. Neither were any om- 

 phalo-mesenteric vessels detectable within the cavity of the ab- 

 domen. But the anastomosis between the veins of the abdominal 



1 Brown-Sequard, 'Journal de Physiologie,' vol. ii. p. 34, 1859. 



2 ' Phil. Trans.,' 1857, P- 34 8 - 





