SKIN-GLANDS. 



203 



tlieir extraordinaiy size, these important organs are merely 

 large sebaceous skin-glands (Plate V. Fig. IG, md). The 

 milk is produced by lic[uefaction of the fatty milk-cells 

 within the branched milk-gland pouch (Fig. 21.3, c), just 

 as the sebaceous matter of the skin, and the fatty matter 

 of the hair are produced by the breaking up of fatty 

 sebaceous cells within the sebaceous skin-glands. The 

 excretory passages of the milk -glands enlarge into sac-like 

 milk-ducts (b), which again become narrower (a), and open, 

 through from sixteen to twenty-four minute apertures, into 

 the nipple of the breast. The first rudiment of this large 

 and complex glaud is a very simple conical plug in the 



Fig. 215. — The breast of the female in section : c, grape-like glandular 

 lobnles ; h, enlarged milk-ducts; a, narrow excretory ducts, opening tL rough 

 the breast-nipple. (After H. Mej'cr.) 



Fig. 216. — Milk-glands of a new-bom child : a, original central gland; 

 h, smaller, and c, larger branches of the latter. (After Langer.) 



