140 THE ALIMENTARY SYSTEM. 



granules, while the protoplasmic zone toward the attached 

 bases of the cells, where the nuclei are situated, is dark, more 

 opaque, and less (or more finely) granular. During secretion 

 the zymogen-granules and clear material distending the cells 

 are discharged ; when exhausted by prolonged activity the 

 cells are thus left shrunken, darker, opaque, and non-granular 

 (or only finely granular). 



Bodies of Langerhans : Between the lobules in places are 

 rounded vascular aggregations of small cells, more open and 

 less dense than the secreting alveoli which make up the bulk 

 of the gland ; these are called the bodies of Langerhans, and 

 are perhaps imperfectly developed lobules, though their nature 

 is not entirely understood. 



