118 MAMMARY APPARATUS OF THE MAMMALIA 



ment observable in the hedgehog. The knob- 

 shaped primordiiim is here likewise hollowed 

 out into a nipple pouch, and then everted to 

 a little nipple, onl}^ the eversion proceeds some- 

 what differently. First of all, the part of the 

 nipple pouch adjoining the cutis wall evaginates, 

 whilst the bottom remains unaltered. At the 

 same time the cutis wall begins to grow up, 

 and in consequence there arises a nipple eleva- 

 tion, on the tip of which the remnant of the 

 nipple pouch forms a small groove, from which 

 the milk-gland buds spring. This groove later 

 disappears through the completion of the ever- 

 sion process. In this wa\^ already during 

 embryonic life the nipple attains its final form, 

 with the separate milk ducts opening on its 

 apex. It is formed chiefly from the nipple 

 pouch ; its basal section is, however, produced 

 by the cutis wall. 



If we now proceed to consider the nipple 

 development in the human subject, on which 

 we have obtained reliable information in recent 

 times, especially through Brouha (1907), we 

 find here an important divergence from the pre- 

 viously discussed types, inasmuch as the knob- 

 shaped primordia are no longer transformed 



