The Ovaries 19 



tion by elaborating the ovum, or egg, which, after being 

 discharged from the ovary and fertilized by the spermato- 

 zoon, becomes a distinct, but in mammalia not immediately 

 an independent, being. The fertilized ovum is still depend- 

 ent for a time upon the oviducts for its transportation to the 

 uterus, upon the uterus for its nutrition and protection dur- 

 ing pregnancy and its expulsion at fetal maturity, and upon 

 the milk from the udder of the mother as food immediately 

 after birth. 



The size, form, and location of the ovaries of domestic 

 animals differ greatly according to species, breed, age, and 

 individual ; even the two glands in the same animal are not 

 ordinarily alike and may vary greatly in size and form. The 

 ovary of the mare is much the largest seen in the domestic 

 animals, reniform, very dense owing to its thick tunica al- 

 buginea, with a smooth surface which is elevated here and 

 there in many cases by the presence near the surface of 

 cysts varying from less than 0.25 inch to 2 or more inches 

 in diameter. The gland attains its maximum size when the 

 animal has reached the age of three or four years, and be- 

 gins to atrophy at ten to fifteen years, to become very small 

 and fibrous as age advances. The ovary of the young mare 

 is usually 3!/2 to 4 inches in its greatest diameter and weighs 

 about 4 ounces, while in the aged it may shrink to IV2 inch 

 in its greatest diameter and in weight to 1/2 ounce. The 

 ovary of the cow is much smaller than that of the mare, 

 varying in its greatest diameter between 0.25 and 2 inches 

 and weighing about 0.25 to 0.5 ounce ; it is oblong and gen- 

 erally regular in outline ; its tunica albuginea is only moder- 

 ately dense. The ovary of the sow is comparatively very 

 large. The numerous ovisacs appear prominently on its sur- 

 face in such a manner that the most superficial of them 

 stand out entirely beyond the general ovarian surface at- 

 tached to the body of the organ by a somewhat constricted 

 neck. The ovary of the cat is very oblong, with pointed ex- 

 tremities, and of a bright scarlet color, with the ovisacs 

 standing out thickly over the surface in a way suggesting 

 a mulberry. 



