THE OESTROUS CYCLE IN THE MOUSE 309 
obliteration through contraction of the characteristics which 
differentiate between the O and D uterus. The anastomosing 
uterine and ovarian vessels were small, the uterus was of medium 
size and anemic. 
Histological examination of cross-sections of the vagina mid- 
way between the cervix and the vulva shows the lumen to be 
small in diameter, with the walls thin, folded, and collapsed. 
Free nucleated epithelial cells and leucocytes are present in 
considerable numbers. There is no basement membrane under 
the epithelium and the deepest layer of the stratum germina- 
tivum shows no distinct cell membrane on the side adjacent to 
the stroma. The epithelium not extensively infiltrated with 
leucocytes is only five or six layers deep and shows no signs of 
cornification (fig. 6). Very few mitoses are to be found. Scat- 
tered leucocytes are abundant in the one or two superficial layers, 
and in several places small clumps are gathered in clear lacunae. 
In general the description of the vaginal epithelium holds 
true for that of the lower cervical canal; there is no basement 
membrane beneath the epithelium, which is five or six layers 
high, and no sign of cornification. 
Cross-sections through the uterine cornua midway between 
their junction and the attachments of the oviducts show narrow, 
slit-shaped lumina indicative of a lack of distention. There 
are very few cells of any sort free in the lumina. The epithelium 
has no basement membrane, the lower parts of its cells stain 
lightly, and cell walls are not readily distinguishable. In many 
places the cells are piled up four to eight layers deep in poorly 
staining syncytial masses. Mitoses are only occasional, being 
present in a few instances in the syncytial masses. ‘The epithe- 
lium is intact everywhere, although it is quite heavily infiltrated 
with leucocytes. Some of the glands show functional activity, 
as evidenced by slight distention. 
The oviducts were adherent to the periovarian sacs and were 
sectioned serially with the ovaries. 
The oviducts are moderately distended throughout, and are 
entirely free from leucocytic infiltration. The non-ciliated 
epithelium, lining the second and third portions, shows few signs 
