THE OESTROUS CYCLE IN THE MOUSE 315 
tion before death. It contains a small number of detached 
cornified epithelial cells which are very thin in cross-section. 
A distinct basement membrane clearly marks off the epithelium 
from the stroma. The epithelium is eight to twelve cells deep 
under the granular and horny layers, which are now superficially 
placed in all regions. A few shrunken blue staining cells with 
pycnotic nuclei still remain in the deeper parts of the crypts 
between folds in the mucosa. They represent the last stages of 
degeneration of the cells of the prooestrous smear. Mitoses 
are frequent. There are no leucocytes present in the epithe- 
lium (fig. 10). 
The cervical epithelium is six to eight layers high, but shows 
no cornification as yet. Except for these two points, the de- 
Seription of the vaginal epithelium holds good for that of the 
cervix; i.e., it has a clear-cut basement membrane, contains 
frequent mitoses, and is free from leucocytes. 
The lumina of the uterine cornua are moderately distended, 
but contain no cells of any sort. The basement membrane of 
the epithelium is distinct and heavy and the cells are columnar 
(fig. 15)... Mitoses are moderately frequent. No leucocytes are 
to be found in the epithelium. Gland lumina show a slight 
distention pointing to moderate functional activity, but the 
scarcity of mitotic figures indicates little growth. Cell borders 
are distinct and the cells show no degenerative changes. AlI- 
though a few leucocytes are distributed through the stroma, 
only an occasional one is found in the gland epithelium. In 
section, the uterus shows slight hyperemia. 
The oviducts are moderately distended. In the ciliated 
portions nuclear extrusion is still apparent, but to a less degree 
than during the P stage. Consequently, larger surfaces present 
unbroken ciliation. There are no leucocytes present. No ova 
are to be found in the tubes; therefore, if ovulation occurred 
at the last oestrus, this must have been at least four days previous 
to killing. 
There are two sets of normal follicles far enough matured to 
show liquor folliculi. The ten follicles of the first set are the 
largest found in this series of animals. They are all superficially 
