MAMMARY GLANDS 



403 



glands. A basement membrane separates them from the connective tissue 

 which contains many lymphocytes and eosinophilic cells. 



After the birth of the child, the gland cells become larger and are filled 

 with stainable secretory granules and fat droplets; the latter are near 

 the lumen and are often larger than the nucleus (Fig. 415). After two 

 days of lactation, some of the gland cells are flat 

 and empty of secretion. Others are tall and 

 columnar, with a rounded border toward the 

 lumen; often they contain two nuclei. The 

 fat within them is not the result of degenera- 

 tion as in sebaceous glands, nor a secretion pro- 

 duced by the nucleus; it accumulates through 

 protoplasmic activity, and the cell may be filled 

 several times before it perishes. Transitions 

 between low empty cells and columnar forms 

 occur, but mitoses are absent from the lactating gland, 

 sions are numerous during pregnancy. 



Milk consists of fat droplets, 2-5 /x in diameter, floating in a clear fluid 

 which contains nuclein derived from degenerating nuclei, and occasionally 

 a leucocyte or colostrum corpuscle. Free nuclei may be found, and some 

 cells which undoubtedly are to be interpreted as detached from the alveoli 

 of the gland. 



Gland cell. Membrana Oil drops, 

 propria. 



FIG. 415. FROM A SECTION OF 

 THE MAMMARY GLAND OF A 

 NURSING WOMAN. X 250. 



Mitotic divi- 



O 



o.'O 



FIG. 416. A., MILK GLOBULES FROM 

 HUMAN MILK. X 560. B., ELE- 

 MENTS OF THE COLOSTRUM OF A 

 PREGNANT WOMAN. X 560. 



i, Cell containing uncolored fat globu- 

 les; 2, cell containing minute 

 colored fat globules; 3, leucocyte; 

 4, milk globules. 



FIG. 417. FROM A THICK SECTION OF THB MAM- 

 MARY GLAND OF A WOMAN LAST PREGNANT Two 

 YBARS BEFORE. X 50. 



i, Large excretory duct; 2, small excretory duct; 3. 

 gland lobules, separated from one another by con- 

 nective tissue. 



At the end of lactation, the connective tissue, which has become greatly 

 reduced owing to the enlargement of the glands, increases in quantity and 

 the leucocytes reappear; as during pregnancy, they form colostrum cor- 

 puscles. The lobules become smaller and the alveoli begin to degenerate. 



