A414 J. A. MYERS 
ments found in the literature are sufficient to substantiate the 
conclusion that the nipple remains in a rudimentary state 
during the early life of the individual. In the female it takes 
on its adult virgin form during the prepubertal and pubertal 
stages. In most animal forms a rudimentary nipple is present 
in the male at birth; however, it usually remains rudimentary 
throughout life. A more complete discussion on this subject 
may be found in an earlier paper (Myers, ’17 b). 
Epithelial hood 
Immediately peripheral to the basal part of the developing 
nipple of the new-born the basal layer of the epithelium dips 
deeply to form the epithelial hood. Beginning about the second 
week of postnatal life, degenerative changes appear in the central 
part of the attached end of the epithelial hood. Such changes 
apparently have for their purpose the deepening of the groove ~ 
which at first partially and later completely surrounds the base 
of the nipple. 
At the time of birth a very shallow furrow may be seen sur- 
rounding the base of the nipple (fig. 1).. A few days after birth 
this furrow in most cases has nearly disappeared. However, 
on the fifth day an apparently new depression (fig. 12) appears 
around only a part of the base of the nipple. As age advances, 
this depression or groove becomes deeper and extends around 
a greater part of the base of each nipple, until finally about the 
tenth week in some specimens it completely surrounds the base, 
thus forming a definite pocket in which approximately the basal 
half of the nipple rests. 
Hair follicles appear lateral to the furrow surrounding the 
nipple (figs. 2 and 3), but have not been observed within this 
furrow. : 
Through the ten-weeks stage there is no indication of furrow 
or epithelial hood in the male albino rat. 
In 1876, Gegenbaur called attention to the fact that in Mus 
decumanus and Mus musculus the basal part of the nipples lies 
in a pocket-like depression of the integument. Gegenbaur be- 
