292 THE GASTRIC JUICE. 



The lymphatic vessels of the gastric mucous membrane begin rather close 

 beneath the epithelium as bulbous or loop-like formations (d d) , then pass per- 

 pendicularly to the submucosa, where they attain a considerable size (e) through 

 the union of adjacent branches. The nerves are the same as those of the intestine. 

 The submucosa consists of bundles of connective tissue with elastic fibers and 

 embedded fat-cells. 



THE GASTRIC JUICE. 



The gastric juice is a fairly clear, colorless, levorotatory, readily 

 filtered fluid, with a strongly acid reaction, an acid taste and a character- 

 istic odor. From the presence of free hydrochloric acid, it counteracts 

 putrefaction and, in part, fermentation. Its specific gravity, when the 

 stomach is empty (fasting), ranges between 1004 and 1006.5; after the 

 ingestion of food, from 1010 to 1020, and more than 1020 when the 

 production of acid is diminished. Its amount was said by Beaumont, 

 in 1843, from observations upon a human being with a gastric fistula, 

 to be only 180 grams daily. According to Griinewald, in 1853, it 

 was estimated in a similar case to be 26.4 per cent, of the body- weight 

 in twenty-four hours. Finally it was placed by Bidder and Carl 

 Schmidt, after comparative observations upon dogs, as 6| kilograms in 

 the day, corresponding to y-Q of the body-weight. The gastric juice 

 contains : 



1. Pepsin, the characteristic, nitrogenous, hydrolytic ferment or 

 enzyme that dissolves proteids: from 0.41 to 1.17 per cent. 



2. Hydrochloric acid occurs free in the gastric juice: from 0.2 to 0.3 

 per cent. 



3. Lactic acid may also be found, either from fermentation of carbo- 

 hydrates (fermentation lactic acid) or from being dissolved out of the 

 meat of the food (sarcolactic acid). 



Reactions. Hydrochloric acid alone, and in the free state, is identified by 

 Gunzburg's reagent: To a few drops of filtered gastric juice an equal number of 

 drops of a solution of 2 grams of phloroglucin and i gram of vanillin in 30 grams 

 of alcohol are added, and the mixture is evaporated in a porcelain dish over the 

 water-bath, with the development of a rose-red color. Resorcin, 2.5 grams, dis- 

 solved in 50 grams of dilute alcohol, with addition of 1.5 grams of cane-sugar, 

 may be employed in a manner analogous to the foregoing reagent, likewise giving 

 rise to a red color. 



Reaction for Lactic Acid. A freshly prepared blue mixture of 10 cu. cm. of 

 a 4 per cent, solution of carbolic acid, with 20 cu. cm. of distilled water and one 

 drop of ferric chlorid, is colored yellow by lactic acid. To 5 cu. cm. of the gastric 

 juice to be tested i or 2 drops of hydrochloric acid are added, and the mixture is 

 evaporated over a free flame to the thickness of sirup. The residue is extracted 

 with a little ether, is then poured into a reagent glass containing 5 cu. cm. of 

 water, one drop of a 5 per cent, solution of ferric chlorid is added, and the mixture 

 is shaken. A greenish-yellow color appears even when i part of lactic acid in 

 1000 is present. The gastric contents, evaporated to the consistency of sirup, to 

 expel the alcohol, are extracted by shaking with ether. The filtrate, on addition 

 of an alcoholic solution of iodin and being heated, yields iodoform, in consequence 

 of the formation of acetaldehyd from the lactic acid. 



Hydrochloric acid and organic acids together yield the following reactions. 

 To demonstrate the total free acids (those not combined with albumin), Congo- 

 red is used, also in the form of reagent-paper. It indicates the presence of free 

 hydrochloric acid or a considerable amount of free organic acids by becoming blue 

 in color. The same information is afforded by dark-red benzopurpurin, which is 

 changed to a violet color, and also by tropaeolin OO. A little of a concentrated 

 alcoholic solution of the latter, heated with 4 drops of gastric juice in a dish, yields 

 a bluish-violet stain. 



