78 NON-SPECIFIC OR GENERAL DISEASES 



should receive the necessary attention in tlie way of irrigating 

 the sheath hefore and after each service. 



Physiology of Parturition. — Parturition or birth, when 

 occurring in the mare, is designated as foaling; in the cow, 

 calving; in the sheep, lamhing; and in the sow, farrowing. A 

 normal or natural hirth occurs when no complications are present 

 and the mother needs no assistance. When the act is compli- 

 cated and prolonged, it is termed abnormal birth. The length 

 of time required for different individuals of the same species 

 to give birth to their young varies widely. It may require 

 but a few minutes, or be prolonged for a day or more. The 

 cause of this variation in the length of time required for differ- 

 ent animals to bring forth their young, can be better understood 

 if we study the anatomy of the parts and their functions. 



Throughout the pregnant period the expulsion of the foetus 

 is being prepared for. As the foetus develops there is a corre- 

 sponding development of the muscular wall of the womb. The 

 last period of pregiiancy is characterized by the relaxation of the 

 muscles and ligaments that form the pelvic walls, and a relaxa- 

 tion and dilation of the maternal passages. In addition, de- 

 generative changes occur in the structures that attach the foetus 

 to the womb, the normal structures l)eing gradually destroyed 

 by a fatty degeneration. This results in a separation between the 

 fetal and maternal placenta. The contents of the womb begin 

 to affect the organ in the same manner as a foreign body, irritat- 

 ing the nerve endings and producing contractions of the muscles. 

 These contractions of the muscles help greatly in breaking down 

 the attach?nents until finally the labor pains begin in earnest, 

 and the foetus is gradually forced out of the womb, through tlie 

 dilated os and into the vagina and vulva. 



A normal birth is possible, only when the expelling power 

 of the womb is able to overcome the resistance offered by the 

 foetus and its membranes^ the pelvic walls and the vagina and 

 vulva. 



