CH. XXX.] 



THE SALIVARY GLANDS. 



473 



smaller, highly granular cells containing no mucigen ; these mar- 

 ginal cells stain darkly, and generally form crescentic groups 

 (crescents or demilunes of Gianuzzi) next to the basement mem- 

 brane. They do not secrete mucin, but are albuminous cells. 

 After secretion their grannies are lessened. 



In those alveoli which do not secrete mucin, but a watery 



Fig. 396. A port of a section through a mucous gland after prolonged electrical stimula- 

 tion. The alveoli are lined with small granular cells. (Lavdovski.) 



non-viscid saliva (parotid, and some of the alveoli of the human 

 submaxillary), the cells are filled with small granules of 

 albuminous nature. Such alveoli are called serous or albuminous, 



fig. 307. Alveoli of parotid gland. A, before secretion ; B, in the first stage of secretion ; 

 C, after prolonged secretion. (Langley.) 



to distinguish them from the mucous alveoli we have just de- 

 scribed. 



These yield to the secretion its ferment, ptyalin. The 

 granular substance within the cell is the mother substance of 

 the ferment (zymogen), not the ferment itself. It is converted 

 into the ferment in the act of secretion. We shall study the 

 question of zymogens more fully in connection with the gastric 

 glands and the pancreas where they have been separated from 

 the ferments by chemical methods. In the case of saliva we may 



