48 Veterinary Obstetrics 



In all animals ovulation is normally suspended during preg- 

 nancy, but exceptions to this rule occur. 



In some cases the Graafian follicles become over-distended with 

 follicular fluid, their walls are abnormally resistant, the ova tend 

 to perish, while the enlarged ovisacs persist and grow, and ovu- 

 lation does not occur. The presence of such ovarian cysts gen- 

 erally inhibits the ripening and rupture of other follicles and, 

 thus, not only causes sterility (which see) but exerts a profound 

 influence upon the behavior of the animal, tending to cause nym- 

 phomania, or sexual insanity. 



2. ESTRUM. 



Reproduction among higher animals is fundamentally the re- 

 sult of an irresistible sexual desire occurring simultaneously in 

 the male and female and leading to coition. 



The condition is known as estrum in the female and, as related 

 in the preceding section, occurs immediately prior to or concur- 

 rentl}' with ovulation. It finds expression in various ways with 

 different species of animals. In general there is a nervous excit- 

 ability, the external genitals are .swollen and vascular, there is 

 an increased secretion of mucus from the vulva and vagina. In 

 the mare there are frequent emissions of urine in small quanti- 

 ties, especially in the presence of other horses, most of all of a 

 stallion, the vulvar lips are frequently opened and the erected 

 clitoris protruded. In ruminants and the sow the female imitates 

 the copulatory act of the male by mounting other animals of its 

 species. In certain pathologic cases, the cow, especially, does 

 not confine her expressions of sexual desire to her own species, 

 but when affpcted with nymphomania _ may attempt to mount 

 other species of animals and we have known instances where 

 they have even attempted to mount man and subjected him to 

 very serious, danger. 



In all animals there is a tendency for the female to wander 

 from home during estrum. This is most noticeable in carnivora, 

 which, if not securely confined, regularly disappear and tend to 

 wander long distances and remain away during a large part or 

 all of the estrual period. In all animals there is a more or less 

 apparent odor characteristic of estrum and peculiar to the species. 



