226 DIGESTION. 



juice, but his descriptions of the phenomena which accom- 

 pany its secretion have been repeatedly verified. 



During the intervals of digestion, the mucous membrane 

 is comparatively pale, -" and is constantly covered with a 

 very thin, transparent, viscid mucus, lining the whole in- 

 terior of the organ." 1 On the application of any irritation, 

 or, better, on the introduction of food, the membrane 

 changes its appearance. It now becomes red and turgid 

 with blood ; small pellucid points begin to appear in various 

 parts, which are, in reality, drops of gastric juice ; and these 

 gradually increase in size until the fluid trickles down the 

 sides in small streams. The membrane is now invariably 

 of a strongly acid reaction, while at other times it is either 

 neutral or faintly alkaline. The thin watery fluid thus 

 produced is the true gastric juice. Though the stomach 

 may contain a clear fluid at other times, this is generally 

 abnormal, is but slightly acid, and does not possess the 

 marked solvent properties characteristic 'of the natural secre- 

 tion. It has been shown by Beaumont, and his observations 

 have been repeatedly confirmed by experiments on the infe- 

 rior animals, that the gastric juice is secreted in greatest 

 quantity, .and possesses the most powerful solvent properties, 

 when food has been introduced into the stomach by the nat- 

 ural process of deglutition. Under these circumstances the 

 stimulation of the mucous membrane is general, and secre- 

 tion takes place from the entire surface capable of pro- 

 ducing the fluid. When any foreign substance, as the gum- 

 elastic tube used in collecting the juice, is introduced, the 

 stimulation is local, and the flow of fluid is comparatively 

 slight. 2 It has been also observed that the quantity imme- 

 diately secreted on the introduction of food, after a long fast, 



1 BEAUMONT/ op. cit., p. 103. 



2 In endeavoring to obtain the pure gastric juice, Beaumont introduced a 

 gum-elastic tube into the stomach in the morning, when the organ was entirely 

 empty. Obtained in this way, it always required ten or fifteen minutes to collect 

 from one and a half to two ounces of fluid. (Op. tit., p. 106.) 



