GROWTH-CHANGES IN MAMMARY APPARATUS OF DASYURUS. 197 
the presence of numerous sebaceous and sweat-glands, which, 
even in the resting pouch, are larger than those in other parts 
of the body. They undergo marked hypertrophy during 
pregnancy, and it is an interesting fact that this hypertrophy 
runs fairly parallel with that of the mammary apparatus, but 
slightly in advance of it. Fig. 2 shows a typical section 
through the teat region of the pouch, with the mammary 
glands in repose, and gives a good idea of the relation 
between these and the sebaceous and sweat glands overlying 
them. The inner side of the whole gland is limited by the 
musculature of the body wall, and also by the cremaster 
muscle, while the various groups of tubules, both of the 
sweat glands and of the lobules of the milk gland, are 
embedded in a characteristic adipose tissue. 
Yon Ebner (49) describes the lining of the milk-gland 
tubules as single-layered in man, and Lane-Claypon and 
Starling (31) also describe a simple epithelium in the case of 
the virgin rabbit. According to Benda (5), however, this 
epithelium is two-layered in the external parts, but becomes 
single in the deeper parts of the gland, and finally 
Brouha (10) has described in the domestic cat, the rabbit, 
and the bat, the epithelium lining these tubules as double 
throughout. From my own observations I am able to con- 
firm this latter statement with regard to the domestic cat. 
As in the foetus, so in the adult Dasyurus, all the branching 
tubules of the mammary gland are lined by a double layer of 
cells, at any rate in the resting animal, and for some time 
after ovulation (fig. 13 ). The true secretory alveoli of the 
gland with their simple epithelial lining do not make their 
appearance until the last few days of pregnancy or until 
some time after ovulation when this has not been followed 
by fertilisation. 
These observations are in harmony with Benda’s conclusion 
that — te The epithelium of the glandular ramifications of the 
adult mammary gland in repose is composed of a double 
layer of cells.” 
The internal layer presents the appearance of a typical 
