988 



GENERATIVE APPARATUS. 



Sheep rut twice; the Cat, Bitch, and Sow, two or three times ; and the Rabbit 

 and Guinea-pig, eight or twelve times, in the course of the year. The condition 

 lasts in the Mare atid Cow from two to four days, and in the Sow and Bitch 

 from six to ten days. During this period the females have a peculiar smell, by 

 which the males are attracted, even from long distances.) 



Rupture of the Graafian vesicles. — After pubsrty the ovary becomes vascularized, 

 and a certain number of Graafian vesicles increase in volume. At the period of 

 oestrum, one or more of these, according to the species, participate in the change 

 in the ovary, become vascular and distended, and finish by rupturing and 

 evacuating the discus proligerus and ovum. The latter is received into the 

 Fallopian tube and conveyed towards the uterus. 



Corpus luteum. — After the rupture of a Graafian vesicle, its cavity is filled 

 by a clot of blood, which gradually contracts and loses its colour ; at the same 

 time the tunica fibrosa becomes hyoertrophied, and the membrana granulosa is 

 wrinkled and transformed into cylindrical epithelium. To this period of 

 progression succeeds one of regression, during which the cylindrical cells become 

 infiltrated with fat and are graduall absorbed. The term corpus luteum is 

 given to the cicatrix resulting from the rupture of a Graafian vesicle. 



Fig. 533. 



CONSTITUKNT PARTS OF A KAMMA.LIAN OVUM. 



Fig. 532, Entire ovum. Fig. 533, Ovum ruptured, with the contents escaping: m», vitellioe 

 membrane; j, yolk ; vg, germinal vesicle ; tg, germinal spot. 



The progress of the phenomena of hypertrophy and regression is much slower 

 when the escape of the ovum has been followed by impregnation ; so that we 

 have false corpora lutea (those which are independent of pregnancy), and true 

 corpora lutea, those of gestation, and which do not disappear until several weeks 

 after parturition. (The true corpora lutea are recognizable, after parturition, 

 as small white or dark-coloured masses — the corpora albicans vel nigrum. The 

 yellow colour, to which they owe their name, is due to the infiltration of the 

 cylindrical cells with fat.) 



During early life the Graafian follicles are not inert, as has been believed, but 

 are active ; only instead of rupturing and throwing their contents into the 

 Fallopian tubes, after attaining their full development they shrivel, become 

 atrophied, and eventually nothing is left of them except a very small yellow 

 body. 



Such are, very briefly, the functions of the ovary. 



(Beneath the hilus of the ovary, and between the layers of the broad liga- 

 ment and the round ligament, is found a small body, usually described as the 

 parovarium or epoophoron, consisting of a number of fine tubes or tortuous cauala 



