THE GASTRIC JUICE. 129 



mucin-peptones, which have resulted during the digestion of the 

 mucous membrane. 



Purer forms may possibly be obtained according to KUHNE'S 

 METHOD. To this end, pigs' stomachs are placed in large quantities 

 of dilute hydrochloric acid, and are allowed to digest for several 

 weeks. As soon as albumoses are only present in comparatively small 

 amounts, owing to their transformation into peptones, the solution is 

 saturated with ammonium sulphate. In this manner the remaining 

 albumoses, and with them the pepsin, are precipitated. This mass 

 is then further treated with hydrochloric acid and allowed to 

 stand, when a further portion of the albumoses is transformed into 

 peptones. By repeating this process all the albumoses are finally 

 peptonized, and ultimately a nearly pure pepsin is thrown down 

 by saturating with the salt. This is dissolved in water, dialyzed, 

 and finally precipitated with strong alcohol, and rapidly collected 

 on a filter. 



Instead of using the stomachs of animals, some of the more 

 active commercial products may be directly employed and purified, 

 as just described. 



Such preparations give scarcely any of the characteristic color- 

 reactions of the albumins, and are not precipitated by tannic acid. 



Quantitative Estimation of Pepsin. Accurate methods for the 

 quantitative estimation of pepsin are not available. Relative values, 

 however, can be obtained by the following method, as suggested by 

 Hammerschlag : three Esbach tubes (albuminimeters) are em- 

 ployed. Tube 1 is filled to the mark U with a mixture of 10 c.c. 

 of a 1 per cent, solution of serum-albumin in 0.4 per cent, of 

 hydrochloric acid and 5 c.c. of filtered gastric juice. Tube 2, 

 which is the standard, is filled to the same mark with the serum- 

 albumin solution, but receives in addition 0.5 gramme of pepsin. 

 Tube 3 contains merely 10 c.c. of the albumin solution and 5 c.c. 

 of distilled water. Esbach? s reagent, which consists of 10 grammes 

 of picric acid and 20 grammes of citric acid, dissolved in 1000 

 c.c. of distilled water, is then added to each tube to the mark R. 

 After twenty-four hours the amount of precipitate is read off 

 and the difference between tubes 1 and 3 compared with that of 

 tube 2. 



Pepsinogen. The presence of pepsinogen in the gastric juice 

 can be ascertained only when hydrochloric acid is absent, as it is 

 otherwise transformed into the active enzyme. Its occurrence, as 

 such, is hence essentially a pathologic phenomenon, and indicates the 

 absence of free hydrochloric acid. But while the latter may be 

 absent in many diseases which are not associated with structural 

 abnormalities of the gastric mucous membrane, pepsinogen, and con- 

 sequently also pepsin, are found lacking only in disease of the 

 stomach itself, and when complete atrophy of the glandular struct- 

 ures has occurred. 



Test for Pepsinogen. Specimens of gastric juice in which pepsin- 



