PREGNANCY, OR GESTATION. 



By the t6rm gestation we comprehend that period of time dur- 

 ing which tiie young is undergoing development in the uterus of 

 the mother, k periodextending from the time of the fertilization of 

 the ovum until the birth of the fetus. 



The modifications which necessarily take place during this 

 period are of a very profound character, and exert an im- 

 portant influence upon the life and nutritive powers of the 

 mother. 



The volume of the uterus becomes very greatly increased. The 

 walls of the non-gravid organ are contracted and firm and its 

 cavity is insignificant, the mucous membrane of the walls being 

 in contact. As soon as impregnation occurs, the uterus must 

 become very greatly increased in volume in order to accommodate 

 the fetus and its membranes. Even prior to impregnation, during 

 estrum, the uterus has undergone some degree of enlargement 

 and intensified function preparatory to the fertilization and 

 nutrition of the ovum. Con.sequently, impregnation in a way 

 continues and accelerates this increase in volume until it 

 reaches its maximum at the time of parturition. 



The first notable change in the uterus, which has already been 

 anticipated during estrum, is the greatly increased vascularity 

 of the organ, both of the walls and the mucosa. The mucous 

 membrane becomes especially vascular, as is shown by its deeper 

 color and its great increase in thickness, as well as by a softening 

 of the membrane. 



The increased function in the mucosa is not equally apparent in 

 all parts, but is most pronounced in those regions where the 

 attachment of the fetal placenta is to occur. Thus, in the 

 ruminant, the principal increase in activity and growth of the 

 mucosa is at those points which are to constitute the cotyledons 

 of the gravid horn, while, in the mare, it is more evenly distri- 

 buted over the entire organ. In the bitch and cat, it is largely 

 concentrated in that part which is to enter into relations with 

 the placental zone of the fetus. 



In muciparous animals, like the bitch, cat and sow, the 

 uterine cornua become enlarged and bulged at the points where 

 the impregnated ova have lodged and become attached to de- 

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