42 INTERNAL SECRETIONS OF THE OVARY 



(128) think that it is probably on the second day. The ova 

 reach the uterus in about four days, and, if fertihzation has 

 taken place, become implanted eight to ten days after ovula- 

 tion. The corpus luteum attains its maximum size in the non- 

 pregnant animal in about ten days, at which time it is 8-9 mms. 

 in diameter. The corpus luteum of pregnancy may enlarge to 

 a diameter of lo-ii mms. 



CEstrus 



CEstrus 



Days 2 4 6 8 10 i: 14 16 lb 20 22 24 26 28 30 32 34 36 38 40 42 



Fig. 1 8. — Diagram of Ovarian Cycle in Non-Pregnant Sov\\ 



(From Corner). 



At about the tenth day after ovulation in the non-pregnant 

 animal a comparatively sudden regression takes place in the 

 corpus luteum, which in two or three days shrinks to less than 

 half its previous volume, largely owing to the disappearance of 

 the granulosa lutein cells. This degeneration is followed by the 

 growth of the next group of follicles. The ovarian cycle in the 

 unmated animal is shown by Corner as in Fig. i8. 



The changes in the uterine mucosa corresponding to the 

 ovarian cycle have been studied in detail by Corner. During 

 oestrus the cells are of low columnar type and are closely packed 

 together. Mitosis is frequent, and the mucosa has the appear- 

 ance of active proliferation. The glands, however, do not show 

 this. The sub-epithelial connective tissue is crowded with 

 polymorph leucocytes. The uterine stroma is oedematous. 



During the first week after cestrous growth, a further pro- 

 liferation takes place in the mucosa cells, which, by the end of the 

 first week, have become columnar. There is also a burst of 

 mitosis in the gland cells, beginning three to four days after 



