44 Veterinary Obstetrics 



The young of carnivora are born in a very immature state, while 

 those of ruminants and solipeds are well developed and early 

 ready to follow their dams at will. 



In each case, there are probably advantages to the mother and 

 offspring. The rabbit must depend wholly upon flight for pro- 

 tection against foes and would evidently suffer a serious disad- 

 vantage from a greatly increased body weight due to the presence 

 in the uterus of a number of very large fetuses ; the bitch, in 

 the natural state, must depend upon the chase for her food, and 

 she too would be hampered by a great weight due to ,well devel- 

 oped fetuses. 



Reproduction is a complex physiologic process, accompanied by 

 or associated with phenomena which bear an important relation 

 to each other. In approximately the following order, we observe 

 the maturation of the ovisacs or Graafian follicles: estrum, copula- 

 tion, rupture of the Graafian follicles, fecundation and possibly 

 menstruation. The chain of phenomena is finally completed by 

 pregnancy, parturition and the nutrition of the new-born. 



Maturation of the Graafian Follicle. — Ovulation. 



Recounting briefly our previous allusion on page 1 1 to the forma- 

 tion of the ovaries and their specific function , the formation of ova, 

 there is observed very early in embryonic life the two genital 

 ridges forming along the median .side of the Wolffian bodies. Con- 

 sisting at first of a mere thickening of the peritoneum, chiefly due 

 to an elaboration of its epithelium, the external cell layer be- 

 comes columnar in contrast to the surrounding squamous cells, 

 while the deeper strata assume a more or less cuboidal form, to- 

 gether constituting the germinal epithelium. This continues to 

 thicken and certain of the cells become distinctly larger than 

 the others, to constitute the primitive ova, while the deeper epi- 

 thelial layers are being broken into irregular columnar masses, 

 or egg columns, through the growth among them from below of 

 blood vessels and connective tissue. Prior ta birth in those 

 j'oung which are born in a well developed state, shortly after 

 birth in the immature young like that of the rabbit, some of the 

 primitive ova become materially changed, to o.ous'dtMX.e. permanent 

 ova. 



In the process of development the connective tissue stroma 

 throws out a thin layer, the tunica albtiginea, parallel to the sur- 



