CH. XXX.] 



THE MAMMAKY GLANDS 



485 



A few years ago it was stated that human casein ogen will not 

 curdle with rennet ; but this ha^ been shown to be a mistake. The 

 conditions of rennet curdling are somewhat different in the two kinds 

 of milk we are considering, but provided the reaction in the stomach 

 is acid, human milk is curdled by rennet when acted on by gastric 

 juice. 



The Mammary Glands. 



The mammary glands are composed of large divisions or lobes, and these are 

 again divisible into lobules ; the lobules are composed of the convoluted and dilated 

 subdivisions of the main ducts held together by connective tissue. Covering the 

 general surface of the gland, with the exception of the nipple, is a considerable 

 quantity of fat, itself lobulated by sheaths and processes of areolar tissue (fig. 339) 



I 



FIG. 339. Dissection of the lower half of the female mamma, during the period of lactation. <j. In the 

 left-hand side of the dissected part the glandular lobes are exposed and partially unravelled ; 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 towards the nipple 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.) 



connected both with the skin in front and the gland behind; the same bond of 

 connection extends 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 lactiferous 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 ; and during the 

 period of active secretion by the gland, the dilatations form reservoirs for the milk, 

 which collects in and distends them. The walls of the gland-ducts are formed of areolar 

 frith some unstriped muscular tissue, and are lined internally by short columnar and 

 near the nipple by flattened epithelium. 



