228 DIGESTION. 



rious fact that in some animals, particularly when they are 

 very hungry, the sight and odor of food will induce secretion 

 of gastric juice. 1 



The gastric juice is probably one of the most sensitive of 

 the secreted fluids to disturbing influences. It was remarked 

 by Beaumont that a febrile condition of the system, the de- 

 pression resulting from an excess in eating or drinking, and 

 even purely mental conditions, such as anger or fear, viti- 

 ated, diminished, and sometimes entirely suppressed the se- 

 cretion of the stomach. At some times the mucous mem- 

 brane became red and dry, and at others it was pale and 

 moist. In such morbid conditions, it is stated that drinks 

 were immediately absorbed, but that food remained in the 

 stomach undigested for twenty-four or forty-eight hours. 2 



It has also been shown by Bernard and others that vari- 

 ous foreign substances circulating in the blood readily pass 

 into the gastric juice ; and that in cases of organic disease 

 of the kidneys, and in animals in which the kidneys have 

 been extirpated, urea is for a time eliminated by the mu- 

 cous membrane of the stomach. The secretion is always 

 arrested by inflammation or active irritation of the mucous 

 membrane. 



The influence of the nervous system on the secretion of 

 gastric juice, exerted particularly through the pneuiiio-gas- 

 tric nerve, is very marked and important, but its considera- 

 tion belongs properly to the section on the nervous system. 



After the food has been in part liquefied and absorbed 

 and in part reduced to a pultaceous consistence, the secre- 



1 There is considerable difference in different dogs as regards the facility with 

 which the flow of gastric juice may be excited. In some, the stomach is entirely 

 free from fluid during the intervals of digestion, and the gastric juice can only 

 be made to flow by the introduction of some "digestible article. Dr. Dalton men- 

 tions an example of this kind (Human Physiology, Philadelphia, 1864, p. 137). 

 In others, however, the reaction of the stomach is always acid, though it contains 

 hardly any fluid during the intervals of digestion, and an abundant secretion of 

 gastric juice may be induced by very slight stimulation. 



2 Op. tit., pp. 107, 108. 



