266 PHYSIOLOGICAL CHEMISTRY 



be accomplished as follows : The subject eats only a cup of clear 

 tea and two pieces of dry toast for breakfast. One and one-half 

 hours after breakfast, his stomach contents are pumped out by 

 means of a stomach pump. Ten c.c. portions of this liquid are 

 titrated with N/10 alkali using phenolphthalein as indicator. 

 This gives total acidity. 



Free hydrochloric acid may be determined by titration with 

 N/10 alkali using ToepferV reagent as indicator, or by the 

 Guenzberg reagent method described above. The gastric con- 

 tents may be tested for blood by the guaiac test (as performed 

 in the study of -hemoglobin). 



d. Ferments. The gastric juice contains two or perhaps 

 three ferments: pepsin, rennin and lipase. 



II. Digestive Action of Gastric Juice. 



a. ON PROTEINS. A satisfactory method for the study of the 

 digestive action of gastric ferments on proteins is the use of 

 Mett's tubes. Mett's method consists in suspending in a 

 digestive mixture short glass tubes filled with coagulated egg 

 albumin. After incubating, the length of the column of al- 

 bumin which has been digested is observed, and the activity 

 of the digestion mixture judged accordingly. 



1. Preparation of Mett's Tubes. 



White of egg is beaten to break the reticulum, strained 

 through linen or muslin, and allowed to stand until free from 

 air bubbles. The egg white is then drawn up into lengths of 

 glass tubing having an inner bore of 1-3 mm. The tubing is 

 then placed on a wire gauze so arranged that it can be lowered 

 into the inner compartment of a double boiler. The water in 

 the double boiler is heated until that in the inner compart- 

 ment reaches a temperature of 85 C. The gauze is then low- 

 ered into the water and allowed to remain until quite cold. 

 The tubes of coagulated albumin may be preserved by covering 

 the ends with shellac. For use, the tubes are cut into 2 cm. 

 lengths, breaking the tube sharply to get an even edge of 

 albumin. 



