218 GASTEIC DIGESTION. 



week without interfering with the character of the secretion or injuring the 

 health of the animal. 



Although instances of gastric fistula in the human subject had been re- 

 ported before the case of St. Martin and have been observed since that time, 

 the remarkably healthy condition of the subject and the extended experi- 

 ments of Beaumont have rendered this case memorable in the history of 

 physiology. This is the only instance on record,, in which pure, normal gas- 

 tric juice has been obtained from the human subject ; and it has served as 

 the standard for comparison for subsequent experiments on the inferior 

 animals. 



Artificial gastric juice, prepared by extracting the active principle from 

 the mucous membrane of the stomach of different animals and adding hydro- 

 chloric acid, is useful in observations with regard to the chemistry of the 

 peculiar ferment, but fluids prepared in this way are not absolutely identical 

 with the natural secretion. Extracts of the mucous membrane were made 

 by Eberle (1834), Von Wittich, Briicke and many others. 



Secretion of the Gastric Juice. According to Beaumont, during the in- 

 tervals of digestion, the mucous membrane is comparatively pale, " and is 

 constantly covered with a very thin, transparent, viscid mucus, lining the 

 whole interior of the organ." On the application of any irritation, or better, 

 on the introduction of food, the membrane changes its appearance. It 

 becomes red and turgid with blood ; small pellucid points begin to appear 

 in various parts, which are drops of gastric juice ; and these gradually in- 

 crease 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. Although the stomach may contain a clear fluid at 

 other times, this secretion generally is abnormal. It is but slightly acid and 

 does not possess the characteristic properties of the natural secretion. It has 

 been shown by Beaumont, and his observations have been repeatedly confirmed 

 by experiments on the inferior 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 natural process of degluti- 

 tion. The stimulation of the mucous membrane is then general, and secre- 

 tion takes place from the entire surface capable of producing 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 compara- 

 tively slight. It has been also observed that the quantity immediately 

 secreted on the introduction of food, after a long fast, is always much greater 

 than when food has been taken after the ordinary interval. 



While natural food is undoubtedly the proper stimulus for the stomach, 

 and while, in normal digestion, the quantity of gastric juice is perfectly 

 adapted to the work it has to perform, it has been noted that savory and 

 highly seasoned articles generally produce a more abundant secretion than 

 those which are comparatively insipid. An abundant secretion is likewise 

 excited by some of the vegetable bitters. 



