536 THE PHYSIOLOGY OF REPRODUCTION 



quence of this fact 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 circida- 

 tion is maintained to some extent until the last. In these 

 animals the process of parturition may last for hours. In the 

 mare, on the contrary, dehvery is usually effected very rapidly.^ 

 The foetal membranes may be expelled with the young or be 



Fig. 132. — The Foal in the normal position for delivery, the revolution being 

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

 Veterinary Physiology, Baillifere, Tindall & Cox.) 



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

 and then expels them. 



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 being discharged along with the placenta, 

 while others are born separately.^ 



1 Smith, Veterinary Physiology, 3rd Edition, London, 1907. Fleming, 

 Veterinary Obstetrics, London, 1878. See also Wortley Axe, "The Mare 

 and Foal," Jour. Royal Agric. Sac, Brd Series, vol. ix., 1898, and Leeney, 

 " The Lambing Pen," Jour. Royal Agric. Soc, 3rd Series, vol. vii., 1896. 



* Brumpt, "Parturition ohez le Bat blano," BuU. Soc. Zool., France, vol. 

 xxxii., 1907. The loosening of the placenta and other changes in Tupaia are 

 described by van Herwerden, " Die puerperalen Vorgange in der Mucosa uteri 

 von Tupaia javardca," Anat. Hefie, vol. xxxii., 1907. 



