iS95-] 465 [Miller. 
(b) In the young. 
Peromyscas leucopiLs oinadensln; :i two-thirds grown, sexually 
iininature individual. Tlie method of ])re]>aration was the same 
as in the last. 
Examination with a low power (PI. 5, Fig. 1) shows that the 
groove at the hase of the clitoris is deeper and better defined 
than in the adult. The mass of epithelial cells occupying this 
groove has in sagittal sections approximately the form of a rough 
parallelogram, one side of which is the surface of the epidermis. 
This side and the one parallel to it are subequal in length and 
shorter than the sides running perpendicular to the surface. At 
the corners of the parallelogram farthest from the surface are the 
potential openings of two branched glandular structures, while 
between these lies the site of the future vaginal orifice. 
In general the thickened epidermis in the young animal shows 
the same histological characters that were seen in the adult. 
Here also we find a stratum corneum of Zander's second type. 
It is, however, thinner than in the adult and is made up of rather 
more delicate lamellae. Beneath this is a thin, ill-defined stratum 
granulosum one or two cells in thickness. The cells of the 
Malpighian layer form the mass that fills the groove. They are 
less elongated than in the adult and show a slight tendency to 
vacuolation. In this respect they recall the conditions found by 
Biesiadeki in eczema nodules ('G7, Taf. 3, Fig. 11). 
Although this peculiar epithelial growth closes the vaginal 
orifice even more effectually than a true hymen, it neither 
contains the same histological elements nor occupies the same 
position as that structure. The hymen (cf. Tourneux et Legay, 
'84) is a membrane with epithelial tissue on each surface and 
true dermis Avithin. It is produced mechanically in the develop- 
ment of the vagina by the very rapid increase in caliber of this 
tube immediately beneath the surface, the original orifice retain- 
ing its small diameter. In the tissue just described there is no sug- 
gestion of a similar condition, nor is there the least possibility that 
it arises in a like manner. We have to do here with a purely 
epithelial growth, placed immediately ectad to the region which 
the hymen Avould occupy did it occur, and which involves 
PROCEEDINGS B. S. N. H. VOL. XXVI. 30 MAY, 1895. 
