16 BOVINE OBSTETRICS 



cord. The festal membranes are the chorion, amnion and 

 allantois. 



THE CHORION. 



The chorion, or vascular membrane, is the outer envelope 

 surrounding the foetus and the two inner membranes, and 

 adapts itself closely to the outer surface of the mucous mem- 

 brane of the uterus. Its inner surface is partly loosely united 

 to the outer layer of the allantois and partly closely related to 

 the amnion, viz., that portion opposite the back of the foetus. 

 It has very many blood vessels, which eventually ramify in 

 the placentae. 



The chorion has a greater surface than the mucosa of the 

 fecundated horns. For this reason it is situated in the non- 

 impregnated horn and body of the uterus. When a pregnant 

 uterus and contents, for the sake of demonstration, are placed 

 upon a table, and the wall of the uterus is carefully incised 

 down to the chorion and the incision carried over the whole 

 convexity, one notices that the chorion is folded here and 

 there and that quite a large piece can be removed from 

 the non-impregnated tube. The uterine portion of the chorion 

 in the beginning of the foetal period possesses a number 

 of dark-brown villi. Between these villi the chorion is smooth 

 and transparent. For this reason Franck terms the smooth 

 portion chorion Icevis, and the villous one, chorion vilhsum. 

 Those villi opposite to the cotyledons develop more and more 

 to form the foetal placentse {placentce foetales) ; they belong, 

 therefore, to the chorion. The foetal and maternal placentae 

 are present in equal numbers. They rest upon the chorion, 

 non-pedunculated, and each foetal placenta surrounds the 

 maternal placenta, its outer surface therefore being concave. 

 The size of the foetal placentas varies. The larger ones in the 

 highly pregnant animal are 10 cm. long and 5 to 6 cm. wide. 

 When loosened from the maternal placentae and spread out 

 they have a diameter of 14 cm. and 7 cm. respectively. The 

 smallest ones are of the size of a mulberry. 



The foetal placenta is made up of a number of vascular 



