THE PROCESS AND THE PRODUCTS OF GASTRIC DIGESTION. 299 



cu. cm. are taken, 5 cu. cm. of gastric juice being added to the one and 5 cu. cm. 

 of water to the other. The mixtures are poured into Esbach's tubes up to the 

 mark U. Both tubes are then kept for one hour at a temperature of 37 C after 

 which Esbach's reagent is added up to the level of the mark R, and the amount 

 of the precipitate in both tubes is noted after the lapse of twenty-four hours. Pep- 

 tone is not precipitated. Chronic gastric catarrh and carcinoma yield low digestive 

 values, while hypersecretion of the gastric juice may increase the digestive in- 

 tensity. 



Preparation of Pure Peptone. The diluted digestive solution, freed from albu- 

 minates by boiling, and with an almost neutral reaction, is first saturated, while 

 boiling, with ammonium sulphate, filtered when cool, again heated, after beginning 

 to boil made strongly alkaline by adding ammonia and ammonium carbonate* 

 again saturated in the heat with ammonium sulphate, -filtered after cooling, again 

 heated until the odor of ammonia has disappeared, again saturated with the salt, 

 hot, and acidulated with acetic acid. The fluid, filtered in the cold, contains pure 

 peptone. 



The peptones are undoubtedly those modifications of proteids that 

 are intended, after absorption from the digestive tract, and later through 

 the blood, to be employed to replace the proteids consumed by the pro- 

 cess of metabolism in the living organism. 



If much albumin has already been digested by the gastric juice, the pepsin is 

 precipitated and becomes inactive if some hydrochloric acid is not again added 

 from time to time. Admixture with bile in the test-tube impairs the activity of 

 pepsin; nevertheless the entrance of bile into the stomach causes no permanent 

 derangement, as renewed amounts of pepsin are at once secreted by the gastric 

 mucous membrane. The stomach digests less well food that has not been thor- 

 oughly masticated or properly insalivated. The presence of blood or of serum 

 prevents the action of pepsin, as well as of trypsin and of the lab-ferment. Heated 

 to a temperature of 65 C. the pepsin in the gastric juice becomes inactive, pure 

 pepsin even at a temperature of 55 C. Concentrated acids, alum and tannic acid 

 abolish the process of peptic digestion. Alkalinity of the gastric juice, as, for 

 instance, from the presence of large amounts of saliva, also concentrated solution 

 of alkaline salts, such as sodium chlorid, magnesium sulphate and sodium sulphate, 

 have the same effect, as do also sulphurous and arsenous acids, and potassium 

 iodid; while small amounts of sodium chlorid increase the secretion and favorably 

 influence the action of the pepsin. The salts of the heavy metals, which form 

 precipitates with pepsin, peptones and mucin, disturb gastric digestion. According 

 to Langley and Eakins, alkalies rapidly destroy pepsin, and propepsin less rapidly. 

 Acids (as lactic, acetic and hydrochloric) precipitate the gastric mucus and stimu- 

 late the secretion of pepsin, while the salts of the alkalies have exactly the opposite 

 effect. Alcohol precipitates the pepsin, although this is redissolved on addition of 

 water, so that digestion can then proceed again undisturbed. Agents that hinder 

 thorough saturation of proteids, as, for instance, binding them tightly, or concen- 

 trated solutions of astringent salts, retard digestion. 



The ingestion of half a liter of cool water does not disturb gastric digestion in 

 the healthy individual, though it does when the function of the stomach is de- 

 ranged, while the ingestion of a larger amount impairs the digestive activity of the 

 stomach. The same effect is brought about by strong muscular action. In the 

 horse moderate movement (trotting) assists the digestion of starches in the first 

 hour. Warm compresses over the epigastric region favor gastric digestion 



According to Penzoldt, the digestibility of various proteid articles of food by 

 the stomach is given in the following order. Easily digestible: boiled brain and 

 thymus, pike, sea-fish, carp, oysters, chicken, boiled pigeon, raw scraped beef or 

 veal, wheat-bread, cauliflower, soft-boiled egg (casein, alkali-albuminate) . Digest 

 ible with moderate ease: boiled beef and veal, duck, goose, pork, salt potatoes, rye- 

 bread, rice, tapioca, asparagus, rape-cole, carrots, raw egg, pur6e of legumes. 

 Digestible with difficulty: salmon, salt fish, highly salted caviare, string beans, hard- 

 boiled egg. The digestibility of the different meats, from the more to the less 

 readily digestible, is as follows: veal, lamb, mutton, pork, beef, rabbit, horse. 





