172 



MICROSCOPIC .\^. \TUMY or THE ORGANS. 



secretion. The same secretory function has been supposed to be 

 possessed by the intercalary part. The intercalary part finally 

 passes over into the main glandular lubes. The latter are blind 

 tubes, consisting of a glandular epithelium limited on the out- 

 side by a fibril lar membrana propria, on whose inner surface 

 there are branched cells surrounding the epithelia cells. These 

 are of doubtful origin, and are known as basket cells. 



The gland cells of a serous tubule at rest possess a proto- 

 plasm filled with highly refractive granules. The nucleus is 

 small, shrunken, and irregular in outline. During secretion 



FIG. 127. 



Salivary duct^ 



Intermediate duct-' 





 ^ 



- 

 From a section through a human parotid gland. X 450. 



the cells decrease in size, and the protoplasm, especially in the 

 part near the membrana propria, becomes free from granules. 

 At the inner side the cells still contain a few granules, while 

 the outer part has a plainly reticular structure. The nucleus 

 becomes round and shows a distinct chromatin network 

 (Fig. 130). 



The mucous cells have an appearance varying with the con- 

 dition of their functional activity. The empty cells i. e., those 

 which have been active and have begun to rest are small and 

 contain a granular protoplasmic network. The round or oval 

 nucleus lies near the membrana propria and possesses a well- 



