334 NORMAL HISTOLOGY AND ORGANOGRAPHY. 



simple glandular epithelium become distended with 

 the products of secretion that consist of granules and 

 deposits of fat. The granules liquefy and along with 

 the fat globules are discharged into the alveoli as 

 milk. Many particles of fat are taken up by migra- 

 ting white corpuscles, called phagocytes, which mix 

 with the secretion and thus become converted into 

 the colostrum corpuscles of early lactation. The 

 gland cells after secretion accumulate a second sup- 



Fat cells. 



Connective tissue 



^^K^^^fl' 



land alveoli. 



Fig. 239. Section of a portion of the mammary gland. 



ply, and this process is repeated many times. The 

 secreting cell does not disintegrate as is the case in 

 the sebaceous glands of the skin. 



When the gland is not engaged in the secretion of 

 milk, many of the alveoli shrink up and disappear, 

 while the remaining ones become much reduced in 

 size, and the gland as a whole is smaller. The cells 

 of the alveoli become columnar, resembling the cells 

 that line the ducts. The epithelium rests upon a 



