CHAP, i.] TISSUES AND MECHANISMS OF DIGESTION. 345 



If a piece of a gland which has been secreting for some time, 

 and is therefore a discharged gland, be examined in the same way 

 (Fig. 80 b) the granules are far less numerous and largely confined 

 to the part of the cell nearer the lumen, the outer part of the 

 cell around the nucleus consisting of ordinary ' protoplasmic ' cell- 

 substance. The distinction however between an inner ' granular 

 zone ' next to the lumen and an outer ' clear zone ' next to the 

 basement membrane is less distinct than in the pancreas, partly 

 because the granules do not disappear in so regular a manner as 

 in the pancreas and partly because the outer zone of the mucous 

 cell, as it forms, is less homogeneous than that of the pancreatic 

 call. 



The ' granules ' or ' spherules ' of the mucous cell are moreover 

 of a peculiar nature. If the fresh cell, shewing granules, (either 

 many as in the case of a loaded or few as in the case of a dis- 

 charged cell) be irrigated with water or with dilute acids or dilute 

 alkalis the granules swell up (Fig. 80 a! b') into a transparent 

 mass, giving the reactions of mucin, traversed by a network of 

 ' protoplasmic ' cell-substance. In this way is produced an ap- 

 pearance very similar to that shewn in sections of mucous glands 

 hardened and stained in the ordinary way. 



In the loaded mucous cell in such hardened and stained pre- 

 parations (Fig. 81 a) there is seen a small quantity of protoplasmic 



a 



FIG. 81. ALVEOLI OF DOG'S SUBMAXILLARY GLAND HARDENED IN ALCOHOL 

 AND STAINED WITH CARMINE. (Langley.) (The network is diagrammatic.) 



a, from a loaded gland. 



b, from a discharged gland ; the chorda tympani having been stimulated at short 

 intervals during five hours. 



cell-substance gathered round the nucleus at the outer part of the 

 cell next to the basement membrane ; the rest of the cell consists 

 of a network of cell-substance, the interstices being filled with 



