GASTRIC DIGESTION. 41 



day, filter, and add the filtrate to the remaining 1200 cc. of 

 the dilute hydrochloric acid. 



When the meat residue from the 400 g. of meat is used about 2.5 

 liters of the artificial gastric juice are necessary; with the egg-albu- 

 men from 20 eggs, 2 liters. A glycerin extract of the stomach-lining 

 (about 4 cc. of the extract to a liter of the dilute hydrochloric acid, 

 0.27 per cent.) is also much used for digestion experiments. Kuhne 1 

 recommends to press out the contents of the rennet glands of a well- 

 washed stomach by scraping with a spatula and to digest 10 g. of this 

 paste with 1 liter of hydrochloric acid (containing 0.4 per cent. HC1) 

 for four hours at 40 (Kiihne's "normal gastric juice"). 



It is also recommended to extract the mucous membrane of the 

 stomach directly with hydrochloric acid (0.4 per cent.). When pepsin 

 hydrochloric acid is used the principal product is albumose with but 

 little peptone. When the artificial gastric juice from the stomach- 

 lining is used it is said that more peptone is formed. It may be 

 remarked, however, that the action of the hydrochloric acid extract 

 of the stomach-lining is not uniform and is often very deficient. This 

 is due to the fact that this extract still contains slimy, unknown pro- 

 teids, which greatly contaminate the products. To avoid these, 

 Kiihne 2 recommends a purified gastric juice made as follows: The 

 prepared lining from the fundus of the pig's stomach is heated to 40 

 for six days with seven times the quantity of dilute hydrochloric acid 

 containing 0.5 per cent. HC1. The solution resulting is then saturated 

 directly with ammonium sulphate, when a voluminous, resinous pre- 

 cipitate forms. This is collected, freed from the salt solution as much 

 as possible by pressure, washed quickly with water, and dissolved in 

 dilute hydrochloric acid (0.5 per cent.) which contains 0.25 per cent, of 

 thymol (using five times as much hydrochloric acid as of the stomach- 

 lining originally taken). This solution is again heated for some days 

 at 40 and then saturated with ammonium sulphate. The precipitate, 

 "purified pepsin," is used for digestion experiments by suspending it 

 in the 0.27 per cent, hydrochloric acid, using ten times as much of 

 this dilute hydrochloric acid as of the stomach-lining originally taken. 



When the digestion has continued for two to three days, 

 the mixture being repeatedly stirred or shaken, filter the solu- 

 tion through muslin, heat gently, and neutralize it in a large 



1 Zeitschr. f. Biol. 19, 184. 2 Ibid. 22, 426, 428. 



