SECRETION. ;j()7 



tion extending also from the under surface of the gland to the sheathing 

 connective tissue of the great pectoral muscle on which it lies. The 

 main ducts of the gland, fifteen to twenty in number, called the lactif- 

 erous or galactopJiorous ducts, are formed by the union of the smaller 

 (lobular) ducts, and open by small separate orifices through the nipple. 

 At the points of junction of lobular ducts to form lactiferous ducts, and 

 just before these enter the base of the nipple, the ducts are dilated (fig. 



Fig. 221. Dissection of the lower half of the female mamma, during the period of lactation. 

 % In the left-hand side of the dissected part the glandular lobes are exposed and partially un- 

 ravelled; and on the right-hand side, the glandular substance has been removed to show the 

 reticular loculi of the connective tissue in which the glandular lobules are placed : 1, Upper part 

 of the mamilla or nipple; 2, areola; 3, subcutaneous masses of fat; 4, reticular loculi of the 

 connective tissue which support the glandular substance and contain the fatty masses ; 5, one of 

 three lactiferous ducts shown passing toward the mamilla where they open ; 6, one of the sinus 

 lactei or reservoirs; 7, some of the glandular lobules which have been unravelled; 7', others 

 massed together (Luschka). 



221) ; and, during lactation, the period of active secretion by the gland, 

 the dilatations form reservoirs for the milk, which collects in and dis- 

 tends them. The walls of the gland -ducts are formed of areolar with some 

 unstriped muscular tissue, and are lined internally by short columnar 

 and near the nipple by squamous epithelium. The alveoli consist of a 

 membrana propria of flattened endothelial cells lined by low columnar 

 epithelium, and are filled with fat globules. 



The nipple, which contains the terminations of the lactiferous ducts, 

 is composed also of areolar tissue, and contains unstriped muscular fibres. 

 Blood-vessels are also freely supplied to it, so as to give it a species of 

 erectile structure. On its surface are very sensitive papillae; and around 



