248 CHARLES R. STOCKARD AND G. N. PAPANICOLAOU 



tained in them passes into the lumen of the uterus. A similar 

 bleeding may also occur into the lumen of the vagina. 



The regeneration of the mucosa seems to take place very 

 quickly. About six to ten hours after the above stage the new 

 epithelium is already completely formed. The growth of the 

 new and the falling off of the old epithelium seem to go hand in 

 hand, so that no stage is to be found when the uterus is com- 

 pletely unlined by its epithelial layer. However, one may occa- 

 sionally observe, during the above described fourth stage, lim- 

 ited naked regions from which the old epithelium has been 

 detached before the new has formed. 



The wall of the vagina undergoes somewhat the same de- 

 structive changes as the wall of the uterus except that the des- 

 quamation of the vaginal epithelium does not occur in cell 

 clumps or groups at t.he end of t^e third st0,ge. The vagina 

 merely sheds its epitheUal cells singly but in increasing num- 

 bers from the beginning of the heat period up to the third stage. 

 The desquamation appears to proceed from near the entrance 

 up into the inner portions of the vagina. The cells which ap- 

 pear during the first stage come from near the outer part of the 

 vagina, while during the second stage the desquamated squamous 

 cells are derived from the inner part of the vagina. This state- 

 ment does not include the cornified cells from near the orifice, 

 which are found as mentioned above, between the first and 

 second stages. The vaginal epithelium is also invaded by the 

 leucocytes. This migration is very \dgorous during the third 

 stage, about the same time as in the uterus. An innumerable 

 mass of polymorphonuclear leucocytes migrate into the vaginal 

 epithehum and actually enter its more superficial cells by pene- 

 trating into their ceU bodies (fig. 17). 



The beginning of the desquamation before the massive arrival 

 of the leucocytes shows that the primary cause of the desqua- 

 mation is not the presence of the leucocytes. But, on the con- 

 trary it is probably the presence of the altered and dying des- 

 quamated cells which induces the extensive migration of leuco- 

 cytes to this epithelial surface. The large epithelial cells of the 

 vagina photographed in figure 17 are the same cells which are 



