THE MAMMARY GLAND 



1433 



dilatation, the ampulla (sinus lactiferans} (Fig. 1190). The ampullae serve as reservoirs for the 

 milk. At the base of the nipple the ducts become contracted and pursue a straight course to its 

 summit, perforating it by separate orifices considerably narrower than the ducts themselves. 

 Each orifice (porus lactiferus) is the orifice of a tube which drains an individual gland. The 

 ducts are composed of areolar tissue, with longitudinal and transverse elastic fibres and some 

 muscle tissue derived from that of the nipple; their mucous lining is continuous, at the point 

 of the nipple, with the integument. The epithelium of the mammary gland differs according 

 to the state of activity of the organ. In the gland of a woman who is not pregnant or nursing 

 the alveoli are very small, few in number, solid, and filled with a mass of granular polyhe- 

 dral cells. During pregnancy the alveoli increase in number and enlarge and the cells undergo 

 rapid multiplication. At the commencement of lactation the cells in the centre of an alveolus 

 undergo fatty degeneration, and are eliminated in the first milk as colostrum corpuscles. The 

 peripheral cells of the alveolus remain, and form a single layer of granular, short columnar cells 

 lining the limiting membrana propria. The single nucleus of each cell divides and forms two. 



PECTORALIS MAJOR 



FIBROUS SEPTUM 

 GLAND SUBSTANCE 



ADIPOSE TISSUE 



FIRST 

 RIB 



SECOND 



RIB 

 PECTORALIS 



MINOR 



INTERCOSTALES 

 SHEATH OF PEC- 

 TORALIS MAJOR 



THIRD RIB 



AREOLAR TISSUE 



SUPERFICIAL 

 FASCIA 



LUNG 



ADIPOSE TISSUE 

 HORIZONTAL PLANE 

 OF NIPPLE 



SIXTH RIB 



FIG. 1191. Right breast in sagittal section, inner surface of outer segment. (Testut.) 



In the protoplasm, especially in the end of the cells toward the alveolus, drops of fat appear- 

 and the nucleus toward this end of the cell also becomes fatty. 



The end of the cell toward the alveolus breaks down, and the liberated material constitutes 

 "the albuminous ingredients of the milk, while the drops of fat become the milk globules, 

 portion of the cell which remains forms new cytoplasm, and the same process is repeated over and 

 over ao-ain. The cells also secrete water and the salts which are found in the milk. 



After lactation a number of the alveoli atrophy and disappear, while the remainder become 

 much reduced in size. The gland then consists mainly of adipose and fibrous tissues. 



The fibrous tissue (Fig. 1191) invests the entire surface of the breast, and sends 

 between its lobes, which serve to hold them together. 



The fatty tissue (Figs. 1190 and 1191) surrounds the surface of the gland and occupies the 

 intervals between its lobes. It usually exists in considerable abundance, and determines the 

 form and size of the gland. There is no fat immediately beneath the areola and nipple, 

 i Human Physiology. By Joseph Howard Raymond. 



