ArrEyn.tdKs of thk iw.tus. 



SECTION II.— APPENDAGES OF THE F(ETUS. 



The appendages or annexes, then, comprise the chorion, a membranous 

 envelope exactly adapted to the uterus ; the amnion, a second ovoid 

 sac included within the latter, and containing the fcetus ; the allantoic, 

 a n^embrane composed of two layers, wliich are spread over the external 

 face of the amnion and the inner surface of the chorion, and thus lines 

 the cavity formed by these two envelopes ; a small bladder of a pyri- 

 form shape, the umbilical vesicle ; the jylaccnta, a collection of vascular 

 tufts grafting the fcetus to the mother; and the umbilical cord, com- 

 posed of vessels that attach the foetus to the envelopes which contain it, 

 and which ultimately ramify in the placental tufts. We will describe each 

 of these in detail, as a correct knowledge of their anatomy is essential 

 to the comparative obstetrist. As before, we will take Solipeds as the 

 type of comparison. 



Chokion. 



The cJwrion, the outer envelope proper to the ovum, is found covering 

 it loosely at the earliest period of its existence, and corresponds to the 

 membrane lining the egg in oviparous animals. It is a vast mem- 



Fig. 4r.. 



Chobiox ok thk Mark .\t Mio-tkkm : Inklatkd. 



A, Posterior portion occupying the Body of the Utenis ; V, Left Cornu plicated 

 and sacculated ; C, Right Cornu, longer than the left, and containing a 

 portion of the Fcetus. 



branous sac, completely closed, and which, being moulded upon the 

 uterine cavity, resembles the uterus in form, having a body and two 

 cornua; the latter, however, are not co-extensive witli those of the 

 uterus. When the chorion is distended, its cornua show fine and deep 

 plica; or bulgings, like the caecum ; the cornua are always unequal in 

 size, that in which the fcetus is developed being of course the largest. 

 The external surface, otherwise smooth, is studded witii innumerable 

 small, red, short papilla? or " processes," which are formed by the 

 placental villous tufts. This papillary face adheres slightly to the 

 internal surface of the uterus, and between the two surfaces a trifling 

 quantity of brown or blood-coloured fluid is found. The inner face is 



