200 PHYSIOLOGY AT THE FAKM. 



sion of the chyme or product of ventricular digestion into 

 the duodenum, is mainly for the purpose of subjecting the 

 alimentary mass in every part to the due influence of that 

 secretion. 



As regards the effect of the gastric juice on the aliment, 

 few differences have been remarked between what occurs in 

 the human stomach, which has been chiefly studied, and what 

 takes place in the stomachs of the animals here under particu- 

 lar consideration. 



When the mucous membrane of the human stomach, in a 

 distended state, is submitted to examination, it is found to be 

 smooth, level, soft, and velvety. When allowed to contract, 

 numerous folds or rugae, chiefly longitudinal, are discoverable. 

 Examination of the free surface with a lens brings out a re- 

 markable honeycomb appearance, occasioned by shallow poly- 

 gonal depressions or cells, varying in diameter from the 200th 

 to the 350th of an inch ; increasing, however, near the pylorus, 

 to the 100th part of an inch. Elevated ridges separate these 

 cells from each other, and these ridges sometimes bear minute 

 narrow, vascular processes, more particularly in some morbid 

 conditions of the organ, which have been mistaken for villi 

 like those by which absorption takes place in the small intes- 

 tines. The bottom of each cell exhibits minute openings, and 

 these are the orifices of very small tubes or glands placed per- 

 pendicularly side by side in sets, so close together as to com- 

 pose nearly the whole structure of the mucous membrane. 

 The length or depth of these tubes varies from one-fourth of a 

 line to nearly a line. Their length indeed is proportionate to 

 the thickness of the mucous membrane at different parts of 

 the stomach : near to the pylorus they are both more thickly 

 set and longer than elsewhere. The tubes are of greater 

 diameter at their bases, which rest on the submucous tissue, 

 than at their orifices, their diameter at the base being about 



