Changes in Generative Organs, etc., of Non-Pregnant Dog. 547 



In the Bitch, as in all mammals, ovulation is followed by the formation of 

 the corpus luteum. This structure is usually described as degenerating 

 within a comparatively short period if pregnancy does not supervene after 

 coitus (corpus luteum spurium), but remaining persistent throughout the 

 whole or greater part of gestation when this condition follows (corpus 

 luteum verum). According to Ancel and Bouin, however, in the Babbit, 

 in which ovulation takes place normally as a result of coitus (Heape), there 

 apparently is only one kind of corpus luteum (the corpus luteum verum), 

 which structure can be induced to form experimentally in the absence of 

 pregnancy by employing vasectomised males. Ancel and Bouin have shown 

 that, under such circumstances, (condition of pseudo-pregnancy),* the uterus 

 undergoes glandular development and vascularisation, while the tissue of 

 the mammary glands proliferates rapidly, the hypertrophy continuing until 

 about the 15th day, when the corpora lutea begin to degenerate. O'Donoghue 

 and others have confirmed these results for the mammary gland. The develop- 

 ment of the mammary tissue in the later part of (true) pregnancy is 

 ascribed by Ancel and Bouin to the influence of the myometrial gland, 

 but Hammond has shown that it is far more likely to be due to the 

 continued influence of the corpora lutea, depending upon the presence of 

 the foetus. According to this observer, the corpora lutea do not degenerate 

 in the later part of pregnancy, and, consequently, the corpora lutea of 

 pseudo-pregnancy in the rabbit are comparable to the corpora lutea spuria 

 of most other mammals, although it would seem probable that (when 

 produced) they persist for a longer time, and exert a greater influence than 

 in those polycestrous animals which ovulate spontaneously. 



In the Marsupial Cat (Dasyurus) there is only one kind of discharged 

 follicle, the corpus luteum of pregnancy or pseudo-pregnancy, and the 

 changes which occur in the mammary glands as a result of luteal influence 

 are identical, irrespectively of whether gestation supervenes or not (Hill 

 and O'Donoghue). 



In polyoestrous animals the corpus luteum spurium usually degenerates 

 after a short period, so as to make way for the maturation of new follicles 

 and the process of ovulation at the frequently recurring cestrous periods. 

 Otherwise, the ripening follicles degenerate under the influence of the 

 corpus luteum. Sandes has described follicular atrophy in widening circles 

 around the fully developed corpus luteum of Dasyurus. The more rapid 

 degeneration of the corpus luteum spurium has probably taken place in 



* The term "pseudo-pregnancy," to describe the experimentally produced condition, 

 was first used by Hammond and Marshall, who confirmed Ancel and Bouin's descriptions 

 of the uterine changes occurring under luteal influence in the Eabbit. 



