TYPES OF (ESTROUS CYCLE 



49 



vaginal contents are serous during this stage, which lasts some 

 twelve hours in the normal mouse. 



Qistrus. Towards the end of procestrus the nucleated 

 epithelial cells begin to be mixed with the cornified mucosa cells 

 and the latter gradually supersede the former in the vaginal 

 contents. The cornified cells are typicall}^ non-nucleated and 

 eosinophil at this stage, w^hile the vaginal contents as a whole 

 have a granular appearance. Copulation occurs at this stage, 



Fig. 23. — Vagina of Mouse during Dicestrus. 

 /.;;. leucocytes and nucleated epithelial cells in the lumen. 



usually within the first day. As in the rat, the formation of the 

 vaginal plug from the vesicular secretion of the male provides a 

 reliable means of detecting copulation. The plug, surrounded 

 by an envelope of cornified vaginal epithelium, is shed in about 

 eighteen to twenty-four hours. In the unmated animal this stage 

 lasts about two days and is terminated by the appearance cf 

 leucocytes in the smear. 



Metoestrus. During metoestrus the vagina returns to the 

 dioestrous condition. The smear consists of cornified cells with 

 a gradually increasing number of leucocytes. Finally, nucleated 

 epithelium appears, and the sm.ear becomes of the normal dioes- 

 trous type. 



P.S.O. D 



