SUBLINQUAL GLAND. 121 



on and tend to fill the lumen, contain more granules, and stain 

 less deeply. In the exhausted condition, when the secretion is 

 discharged, the cells are somewhat contracted and smaller, 

 leaving the lumen larger, and appear darker, more opaque, 

 and more deeply stained from the condensation of the proto- 

 plasm. 



In the sublingual gland, which is of the mucous type, the 

 alveoli are rather larger than in the serous parotid, and have 

 a prominent basement-membrane. The cells lining the alveoli 

 are of two kinds, the ordinary mucin-secreting (central) cells 

 and the peripheral or demilune cells. 



Mucous alveoli from submaxillary gland, showing mucinogenous cells and demi- 

 lunes of Heidenhain (Ranvier). 



The former make up much the larger part of the gland and 

 form a single layer of spheroidal epithelium-cells lining the 

 lumen, and (except where the demilunes are situated) resting 

 upon the basement-membrane. These cells are of the type 

 characteristic of mucous glands ; when resting and distended 

 with secretion they are swollen, and except where their body- 

 protoplasm and nuclei are pressed toward the attached bases 

 the cell-bodies are clear, transparent, and do not stain deeply. 

 After exhaustion and discharge of the secretion by prolonged 

 activity, the cells become smaller, less clear and transparent, 

 and the more concentrated protoplasm stains more deeply. 



In places between the mucinogenous or central cells are 



