i88 



HISTOLOGY. 



repeatedly, the epithelium becomes a simple columnar epithelium, after 

 being pseudostratified, with two rows of nuclei (Fig. 27, p. 28). Possibly 

 the epithelium near the outlet of the duct is also pseudostratified. The 

 excretory portion of the duct is followed by the secretory part formed of 

 simple columnar cells with basal striations, perhaps indicative of secretory 

 activity. As shown in the diagram, Fig. 211, and in the sections, Figs. 

 212 and 213, the secretory duct becomes slender, making the intercalated 

 ducts. They are lined by flat cells, longer than they are wide, and these 

 form a continuous layer with the large cuboidal serous gland cells of the 

 terminal alveoli. The gland cells when empty of secretion are small and 





Excretory 

 duct. 



Fat cells. 



End piece. 





Intercalated ,< 

 duct. 



End pieces. 



FIG. 211. DIAGRAM OF THE 

 HUMAN PAROTID GLAND. 





FIG. 212. SECTION OF THE PAROTID GLAND OF AN ADULT 



MAN. X 252. 



The very narrow lumen of the alveolo-tubular end pieces is not 

 shown. 



darkly granular, and when full are larger and clearer. They rest upon a 

 basement membrane containing stellate cells. Intercellular secretory cap- 

 illaries end blindly before reaching the basement membrane. 



The alveoli of the parotid gland are somewhat elongated, and are 

 branched. Between them there is vascular connective tissue containing 

 fat cells. In denser form it surrounds the lobules and lobes of the gland, 

 and the larger ducts. The ducts which are found in the connective tissue 

 septa are called interlobular ducts, in distinction from those which are 

 surrounded by the alveoli in which they and their branches terminate. 

 The latter are intralobular ducts. They are smaller and have less con- 

 nective tissue around them than the interlobular ducts, of which however 



