32 INTERNAL SECRETIONS OF THE OVARY 



mammary tissue in the virgin bitch shows no growth character- 

 istic of prooestrus or oestrus. 



During oestrus, ovulation takes place and the growth phase in 

 the uterus is superseded by a regressive one, which is char- 

 acterized by the breakdown of the capillary walls and the 

 extravasation of blood into the stroma. Aided by a certain 

 amount of destruction of the superficial epithelium, the blood 





poly III./ \®^^ ^ ^ _^\ ^^ 









Fig. 15. — Procestrous Uterine Mucosa of Dog. 



(From Marshall and Jolly). 



ex.bl. extravasated blood corpuscles; polym. polymorph; sec. cells 

 probably indicating secretory activity. 



corpuscles find their way into the lumen of the uterus and thence 

 to the exterior, giving rise to the external bleeding characteristic 

 of early oestrus in the dog. During metoestrus the corpora lutea 

 are beginning to form in the ovary, and the uterine mucosa 

 regenerates. If pregnancy does not occur, pseudo-pregnant 

 changes take place, correlated with the development and 

 persistence of the corpus luteum in the ovary. Pseudo- 

 pregnancy is characterized by considerable enlargement of the 

 uterus and by growth of the mammary glands. Gerlinger 

 distinguishes two layers of the uterine stroma during this period ; 



