262 CHARLES R. STOCKARD AND G. N. PAPANICOLAOU 



the lost epithelium becomes rapidly replaced almost before it 

 has ceased falling away. If one may picture the epithelial sur- 

 face of the uterus and vagina as consisting of innumerable promi- 

 nences and depressions, it may be said that the destructive proc- 

 esses mentioned above are largely confined to the epithelium 

 covering the prominences and that this epithelium is finally 

 restored by regeneration from the epithelium lining the depres- 

 sions, or in the case of the uterus from the epithelium of the 

 uterine glands. The congestion with the diapedesis of cor- 

 puscles and the formation of the blood haematomata and the 

 great accumulation of leucocytes all occur chiefly in the out- 

 pushed or protruding parts of the uterine wall. 



The regeneration process in the guinea-pig is very short, last- 

 ing only a few hours, from six to twelve in all. 



5. Ovulation seems to occur spontaneously during every heat 

 period without exception. The rupture of the follicles with the 

 consequent ovulation takes place about the end of the second 

 stage or the beginning of the third ; that is, during the presence 

 of the thick cheese-like vaginal fluid. 



6. During the dioestrum or intermenstrual period there is very 

 little fluid to be found in the vagina. This scant fluid consists of 

 mucus in which are some atypical squamous cells from the 

 vaginal wall and many leucocytes. A number of the leuco- 

 cytes are old but there are probably new ones arriving almost 

 continuously from the wall of the vagina. The only time at 

 which the vagina seems to be practically Iree of leucocytes is 

 immediately before and during the first and second stages of the 

 oestrous period described above. 



7. A marked correlation exists between the oestrous changes 

 in the uterus and the developmental cycle of the corpora lutea. 

 When the corpora lutea are highly developed and apparently 

 active the mucosae of the uterus and vagina show a normally 

 vigorous and healthy condition. While, on the other hand, 

 when the corpora lutea begin to degenerate during the second 

 week after the 'heat period' the mucosae ot the uterus and 

 vagina also begin to show signs of degeneration and the process 

 of desquamation slowly commences. At about two weeks after 



