INNERVATION OF THE GENERATIVE ORGANS 569 



any difficulty experienced in delivery usually causes the death of 

 the foal. In Ruminants, on the other hand, the separation of the 

 cotyledons takes place very gradually, so that the connection between 

 the maternal and foetal circulation is maintained to some extent 

 until the last. In these animals the process of parturition may last 

 for hours (in the cow, about two hours ; in the sheep, al>out fifteen 

 minutes for each lamb born). In the mare, on the contrary, 

 delivery is usually effected very rapidly 1 (five to fifteen minutes). 

 In the sow, bitch, and cat it takes from ten to thirty minutes for 

 each young one born, with sometimes an interval of an hour between 

 the births. The foetal membranes may be expelled with the young 



FIG. 159. The foal in the normal position for delivery, the revolution being 

 completed and the membranes ruptured. (After Franck. From Smith's 



\','t,-fin,i,-ii riiii*il<xjy, Bailliere, Tindall & Cox.) 



or be retained until a little later, when the uterus recovers its power 

 and then expels them (in the mare several hours after the foal 

 is born). 



In the Carnivora the mother usually gnaws through the umbilical 

 cord but in the other animals it is torn. 



In animals such as the rat, in which multiple conception is the 

 rule, the " presentation " of the young at birth may be either " breech " 

 or " head." The foetuses tend to be expelled irregularly, some l>eing 



Parturition" by the same author in Tin- .V"W<m/ Cyclopedia of Modern 

 Agriculture, vol. ix., London, 1910. 



