PHYSIOLOGY. 



43 



passage, or it may pass outside, without rupture. 

 In any case, it is shortly followed by the two fore- 

 feet of the foetus, with the head resting between them 

 at the fetlocks. When the point of the withers of the 

 foetus appears at the entrance of the pelvic cavity, a 

 few more slight contractions complete parturition. 



Fig. 19. 



Normal Position of the Foetus in the Mare (Third Stage), 



Vertebrosacral Position. 



Parturition is quite a normal function, when 

 performed in the manner described. When the foetus 

 has been fully developed in the uterus, there is a 

 gradual determination of its blood supply to the 

 mammae of the parent. A number of the vascular 

 connections are then no longer needed between the 

 uterus and the placental membranes, and fatty degene- 

 ration of these takes place. This alteration is believed 

 to have some special action on the nerve filaments in 

 the uterine walls, which (filaments) become irritated, and 

 through them the walls of the uterus are stimulated to 



