DIGESTION. 25 



lining the acini of the gland are seen to be filled with fine granules, which 

 are often so abundant as to obscure the nucleus and enlarge the cells until 

 the lumen of the acinus is almost obliterated (Fig. i). When the gland 

 begins to secrete the saliva, the granules disappear from the outer boundary 



FIG. i. 



Cells of the alveoli of a serous or watery salivary gland. A. After rest. B. After a 

 short period of activity. C. After prolonged period of activity. From Yeo's 

 Text- Book of Physiology. 



of the cells, which then become clear and distinct. At the end of the 

 secretory activity, the cells have become free of granules, have become 

 smaller and more distinct in outline. It would seem that the granular 



FIG. 2. 





Section of a u mucous " gland. A. In a state of rest. B. After it has been for some 

 time actively secreting. After Lavdoiusky. 



matter is formed in the cells during the rest, and discharged into the ducts 

 during the activity of the gland. 



In the mucous glands, e. g., sub-maxillary and sub-lingual, the changes 

 that occur in the cells are somewhat different (Fig. 2). During the inter- 



