DIOESTROUS CYCLE IN THE GUINEA-PIG 249 



to be observed in the vaginal fluid during the third stage, see 

 smears figures 6, 7 and 8. A congestion of the capillaries of the 

 mucosa also takes place in the vagina, and slight hemorrhages 

 may occur as in the uterus, when the destruction of the stratified 

 epithelium chances to reach down to the tunica propria. 



The leucocytes are chiefly attracted to that portion of the 

 epithelium covering the outfoldings into the lumen and this part 

 undergoes a greater destruction. In a similar way it is the epi- 

 thelium covering the prominent folds of tjie uterus which is 

 destroyed, while the ingrowths which form the uterine glands 

 are preserved and thi'ough regeneration from their necks furnish 

 the new material which is necessary for the restoration of the 

 lost epithelium. 



During the dioestrum or rest period the desquamation of epi- 

 thelium from the vagina does not stop completely and the scant 

 vaginal fluid always contains some desquamated cells. At the 

 same time, and probably connected with the shedding process 

 the exodus of the leucocytes also continues though in a less 

 active way than during heat. The 'intermenstrual fluid' there- 

 fore always contains a considerable number of leucocytes. 



7. THE OVARIAN CYCLE 



A study of the ovaries fixed during different stages of the 

 oestrous cycle has shown that every change taking place in the 

 uterus and the vagina has its corresponding stage of change in 

 the ovary. At the beginning of the first stage the ovaries 

 possess large, ripe follicles, figures 20 and 21. The nuclei of the 

 eggs contained in the follicles are in a resting condition. The 

 theca folliculi shows the beginning of a slight congestion. As 

 the first stage advances this congestion becomes more and more 

 pronounced and by the beginning of the second stage it is highly 

 developed, figures 22 and 23. This extreme congestion of the 

 theca folliculi, which exist at about the same time as the con- 

 gestion stage in the uterus (cf. fig. 14) indicates that the follicle 

 is ready for rupture. Heape has pointed out that the rup- 

 ture of the follicle is due to this congestion and if the ovarian 



THE AMERICAN JOURNAL OF ANATOMY, VOL. 22, NO. 2 



