DIGESTION 



187 



One of its characteristics is its permanence in the air, putrefaction never 

 occurring. The average daily quantity is hard to determine, but in a 

 man is very likely from two to five liters. In various animals its strength 

 is very different. In the dog, for example, it is about three times as strong 

 as in man, so that this animal can afford to bolt its food. In composition 

 gastric juice probably varies greatly at different times according to the 

 digestive habits of the individual. Schmidt's analyses are quoted as 

 often as any, and it is interesting to compare his determinations of the 

 gastric juice from an omnivorous animal (man), from a carnivorous 

 animal (dog), and from an herbivorous animal (sheep). It is likely that 

 the strength accorded to man's gastric juice is weaker than the average, 

 especially in hydrochloric acid, which may be often 1 or even 2 per cent. 



FIG. 89 



Human gastric mucosa, peptic region, vertical section: a, muscularis mucosse; b, subglandu- 

 lar lymph plexus; c, intraglandular lymph sinus; d, suggestion of an external plexus of lymph 

 channels; /, submucous lymph plexus. (Loven.) 



COMPOSITION OF GASTRIC JUICE (Schmidt). 



The organic matter consists of pepsin, "rennin," lipase, and traces of 

 a proteid and of mucin. Secretion of gastric juice apparently does not 

 continue after the stomach becomes empty. It is readily induced, 

 however, by the introduction of any solid substance into the organ, or 



