DIOESTROUS CYCLE IN THE GUINEA-PIG 239 



serve to indicate an intermediate period between the first and 

 second stages or periods of the flow, and may really be found 

 during both stages but particularly at the end of the first and 

 beginning of the second stage. In addition to these two kinds 

 of cells other types may also be found in a first stage smear but 

 they are never present in such abundance nor are they so typical 

 as the two just mentioned. All of the cells float freely in the. 

 mucus without assuming any definite arrangement. 



During the second stage the vaginal fluid is filled with enor- 

 mous numbers of cells which cause the cheese-like consistency 

 of the discharge at this time. These cells illustrated by the 

 photomicrographs, figures 2, 3 and 4 at three different magnifi- 

 cations, are derived from the upper portions of the vagina with a 

 few from the uterus and they maintain to a higher degree the 

 original or healthy architecture of an epithehal cell. The nuclei 

 are fairly well preserved sho^vdng only slight signs of degenera- 

 tion. The protoplasm has not greatly deteriorated and gives a 

 good staining reaction thus differing from the grey-staining first 

 stage cells. The cells are present in innumerable quantities 

 forming the thick cheesy substance while the mucous secretion 

 diminishes more and more until it almost disappears. This stage 

 is of short duration. 



The third stage begins with the hquefaction of the cheesy mass. 

 A microscopical examination shows that the cells of the second 

 stage become less and less numerous, while a great number of 

 polymorphonuclear leucocytes appear among them (figs. 5 and 

 6). When the end of this process is reached almost every one 

 of the cells has become isolated from others of its kind and lies 

 in the midst of a number of leucocytes. The apparent action or 

 effect of the leucocytes is to dissolve or digest the desquamated 

 epithelial cells and this dissolving effect is not only noticed on 

 cells surrounded by the leucocytes but in some cases the leuco- 

 cytes dissolve their way into the interior of the cell-bodies (figs. 

 7 and 8). 'These appearances are not due, as might possibly be 

 supposed, to the cells having devoured the leucocytes. This 

 destructive influence of the leucocytes begins, as will be de- 

 scribed latqr, before the desquamated epithehal cells have fallen 



