756 THE PLACENTA. 



membrane, and is discharged without any hemorrhage or laceration of 

 the parts. 



In other instances, there is a more intimate connection, at certain 

 points, between the foetal and maternal structures. In the cow, the 

 sheep, and the ruminating animals generally, the external membrane of 

 the egg, beside being everywhere supplied with branching bloodvessels, 

 presents, scattered over its surface, a large number of distinct rounded 

 or oval spots, at each of which it is covered with thickly set, tufted, 

 vascular prominences. These spots are called cotyledons, or cups, be- 

 cause each one is surrounded by a raised rim or fold, which embraces a 

 corresponding rounded mass projecting from the internal surface of the 

 uterus. This projecting portion of the uterine mucous membrane is 

 also abundantly supplied with bloodvessels; and the tufted vascular 

 loops projecting from the surface of the foetal membrane (Fig. 271, 6, 6) 

 dip down into its substance and are entangled with those belonging to 



Fig. 271. 



COTYLEDON, from the pregnant uterus of the cow.-o. Internal surface of the allantois. 

 b, b. Foetal bloodvessels, c, c. Surface of uterine mucous membrane, d, d. Maternal blood- 

 vessels. 



the uterus (d, d). There is no absolute adhesion between the two sets 

 of vessels, but only an interlacement of their ramified extremities ; and 

 by careful manipulation the foetal portion, with its villosities, may be 

 extricated from the maternal portion without the laceration of either. 



In the carnivorous animals, a similar highly developed, vascular por- 

 tion of the allantois runs, in the form of a single broad belt or band, 

 round its middle part ; and this corresponds in situation with an equally 

 developed zone of the uterine mucous membrane. Here the foetal and 

 maternal structures are adherent to each other ; while, elsewhere, 

 toward the two extremities of the egg, they lie simply in contact. 

 When gestation comes to an end in these animals, and the foetus, with 



