542 



THE REPRODUCTIVE SYSTEM 



active only in the event of pregnancy. Upon the hemispherical corpiis 

 mammae can be distinguished the central raised nipple or mammilla, and 

 the surrounding roughened and pigmented circular area, the areola. 



Each mammary gland consists of fifteen to twenty lobes, each of 

 which is of itself a branched saccular gland whose lactiferous duct opens 



FIG. 474. FROM THE ACTIVELY SECRETING MAMMARY GLAND OF A WOMAN. 



Several lobules are included, a, interlobular duct; b, interlobular connective 

 tissue. Hematein and eosin. Photo. X 52. 



on the surface of the nipple near its apex. The main lactiferous or lobar 

 ducts subdivide in an arborescent manner into many interlobular ducts, 

 about which are clustered the groups of secreting alveoli, each group 

 forming one of the many lobules included in a lobe of the gland. The 

 structure of the lobule, as well as the general appearance of microscopi- 

 cal sections of the gland, varies according to the stage of development 

 and the condition of activity of the organ. 



