192 



HISTOLOGY. 



tirely of serous cells. The others are mixed, but the crescents are small, 

 composed of only a few or even of single serous cells. Secretory capillaries 



Excretory 

 duct. 



Blood vessels. 

 Secretory duct. 



Secretory 

 duct. 



Connec- 



Intercalated tive tissue, 

 ducts. 



^ End pieces. 



Serous end piece. Fat cell. 



FIG. 217. DIAGRAM OF THE HUMAN FIG. 218. SECTION OF THE SUBMAXILLARY GLAND FROM 

 SUBMAXILLARY GLAND. A MAN OF 23 YEARS. X 80. 



such as have already been described, are related only to the serous cells. 

 Elastic tissue surrounding the alveoli has been thought to aid in expelling 



Intercalated duct. 



Connective tissue. 



Secretory duct. 



FIG. 219. SECTION'OF THE SUBMAXILLARY GLAND OF AN ADULT MAN. X 252. 



the secretion through the ducts. It is known that the secretion is elimi- 

 nated from the gland cells under high pressure, and so would not be checked 



