THE GASTRIC JUICE AND STOMACH DIGESTION. 161 



detected by its ordinary reactions in the external liquids. It is thus 

 suited for absorption by the mucous membrane of the alimentary canal. 



All the albuminous matters, without exception, which are susceptible 

 of digestion, whether of animal or vegetable origin, are finally converted 

 by the action of the gastric juice into albuminose. They therefore lose 

 their original distinctive properties, and, when fully prepared for absorp- 

 tion into the bloodvessels, are all reduced to the condition of a single 

 substance. 



A further very remarkable peculiarity of the gastric juice is its apti- 

 tude for resisting putrefaction. While other animal fluids, as the saliva, 

 the bile, the pancreatic juice, mucus and blood, enter into putrefaction 

 with great readiness, the gastric juice remains when exposed to the air 

 at ordinary temperatures for many months without developing any 

 putrescent odor or losing its characteristic properties. It becomes 

 somewhat darker in color, and after a time deposits a brownish sediment 

 upon the bottom of the vessel, but it still retains its acid reaction and 

 its power of digesting albuminous matters. Gastric juice will even 

 arrest putrefactive changes when they have already begun in organic 

 substances ; and consequently putrefaction does not go on in the living 

 stomach. Dr. Beaumont preserved some fragments of meat unaltered for 

 a month in gastric juice, while other portions of the same substances, 

 kept in saliva, were putrefied in ten days. Spallanzain found in the 

 stomach of a viper the body of a lizard which had remained there for 

 sixteen days without undergoing any putrefactive alteration ; and similar 

 observations have been made by other physiologists. 



Mode of Secretion of the Gastric Juice. As a rule, the gastric juice 

 is not a constant but an occasional secretion, being poured out only when 

 food is taken into the stomach. Dr. Beaumont found it to be entirely 

 absent during the intervals of digestion, the stomach containing at that 

 time no acid watery fluid, but only a little neutral or alkaline mucus. 

 He was able to obtain a sufficient quantity of gastric juice for examina- 

 tion, by gently irritating the mucous membrane with a gum-elastic 

 catheter, or the end of a glass rod, and by collecting the secretion as it 

 ran in drops from the fistula; and on the introduction of food he found 

 'that the mucous membrane became turgid and reddened, a clear acid fluid 

 collected everywhere in drops underneath the layer of mucus lining the 

 walls of the stomach, and was soon poured out abundantly into its 

 cavity. Prof. F. G. Smith, in his subsequent observations upon Alexis 

 St. Martin, also found the fluids obtained from the empty stomach 

 invariably neutral in reaction ; while during digestion, whatever might 

 be the nature of the food, they were always acid. Other observers, in 

 experimenting upon the dog, have found more or less acid reaction 

 always present at the surface of the mucous membrane. According to 

 our own observations, the irritability of the gastric mucous membrane, 

 and the readiness with which the flow of gastric juice may be excited, 

 varies considerably in different animals, even in those belonging to the 

 same species. In experimenting with gastric fistulas on different dogs, 



