The Ovaries 21 



and abnormally at times passes out through the inguinal 

 ring and comes to rest in that part of the perineal region 

 corresponding to the scrotum of the boar. The same dis- 

 placement of the ovary occurs rarely in bitches. It is 

 possible in any species. In general it may be said that in 

 the elongated uteri of multiparous animals the ovaries are 

 situated further forward than in the uniparous or biparous 

 genera. The location of the ovary is further modified by 

 the pregnant state. The gravid uterus, in its descent, 

 drags the gland downward and forward. It is also drag- 

 ged downward and forward by any increase in weight due 

 to disease of the uterus, oviducts, or ovary, such as pyome- 

 tra, tumors of the uterus, oviducts and ovaries. 



The functional activity of the ovary modifies its size and 

 form. During the breeding life of the animal the cortex, 

 or peripheral area, of the ovary is largely composed of egg 

 columns, or masses, consisting of germinal cells arranged 

 in the form of a hollow sphere. Resting upon an intruding 

 mass of genital cells is a specially developed cell, the ovum. 

 The spheroidal hollow mass of cells contains a fluid, the 

 follicular liquid. When an ovum, or ova, matures and an 

 ovisac ripens, the female is in estrum or "heat." The 

 ovisac becomes distended with follicular fluid, presses aside 

 the superposed ovarian tissues, and attenuates or destroys 

 the tunica albuginea at the involved point. In most ani- 

 mals the active ovisac pushes its way above the general 

 ovarian surface as a hemispherical cyst with very thin 

 walls. In the mare it regularly protrudes at the hilus of 

 the gland, where it is not readily apparent. The ripe ovisac 

 — or ovisacs — ruptures at the close of estrum, producing a 

 lesion, which usually behaves differently according to 

 whether the discharged ovum becomes fertilized and un- 

 dergoes development into a fetus or, failing of fecundation, 

 perishes. The crater resulting from the rupture of the sac 

 becomes filled with lymph, blood, or other products of the 

 disturbances of the tissues. Should the ovum perish, the 

 lesion tends to heal rapidly, the blood and lymph in the 

 crater are resorbed, and from its walls there forms a char- 

 acteristic tissue, known as the corpus luteum of estrum. 



