170 PKACTICAL HISTOLOGY [XXI 



masses, usually neither the outlines of the cells nor the lumina are 

 seen, the pyloric glands are non-granular and the cell outlines may be 

 visible. The gastric gland-cells in the frog are not so coarsely 

 granular as those of the newt. 



Observations in the fresh state after removal from the body. In the 

 newt, frog, small fish, mouse, guinea-pig and other small animals, 

 the mucous membrane is washed or even scraped, the stomach pinned 

 out over a hole in a stage, the muscular coat removed, the pins re- 

 adjusted so as to stretch the membrane further, a cover-slip is put 

 on, without salt solution unless it is necessary ; the ends of the glands 

 can then be examined under a high power. Or the muscular coat 

 may be removed, and the mucous membrane spread out on a slide. 

 When the mucous membrane is thick, small pieces are cut out 

 (cp. 3). In the guinea-pig and rabbit the granularity of the 

 chief-cells diminishes from the fundus to the pyloric region. 



Changes in digestion. If the small newt (Triton taeniatus) is fed 

 with a worm, digestive changes can be observed in 1 to 3 hours after 

 feeding, the return to the normal state is rapid, it is usually complete 

 in 5 to 10 hours. 



In Triton cristatus the granules rarely disappear sufficiently 

 during digestion to leave an outer homogeneous zone. 



In the frog the digestive period is longer, a marked outer non- 

 granular zone is formed in the oesophageal glands in 3 to 6 hours, 

 but the recovery may take 1 to 4 days. The rate of digestion and the 

 rapidity of the change in the cells varies with the condition of the 

 animal and with the time of year. 



In mammals the formation of zones occurs in the chief-cells only, 

 it is not infrequently less marked in the fundus than in the greater 

 curvature. In the gastric glands of frog and snake an outer 

 non-granular zone is not formed, but the granules during digestion 

 become smaller and less numerous. 



It is to be remembered that if an animal is kept without food 

 longer than the normal digestive period, the granules begin to dis- 

 appear from the gastric cells, so that in a fasting animal the cells 

 may have an outer non-granular zone and present the other characters 

 of secretory activity. 



In observing the changes which take place during digestion the 

 animals taken should be as much as possible alike, and they should 



