90 COMMERCIAL ' PEPSINS/ ACID OF GASTRIC JUICE. [BOOK II. 



Commercial Various preparations have been sold in commerce 



preparations under the name of Pepsin. Officinal pepsin has in 

 of pepsin. many cases consisted merely of the dried mucous mem- 



brane of the stomach of the pig reduced to powder and mixed with 

 starch or milk-sugar. Some has consisted of a product made 

 essentially by Wasmann's method (see p. 85) mixed with large 

 quantities of starch or sugar. One of the most active of the prepara- 

 tions of commerce is made by a method devised by Schaffer, and 

 which rests upon the following facts. If to artificial gastric juice 

 sodium chloride be added in large quantities, the albumoses which 

 are held in solution are precipitated and rise to the surface as a 

 scum, which may be ladled off; this scum is however rich in pepsin, 

 which is mechanically retained by the albumoses as it is by the 

 calcium phosphate precipitate in Brlicke's process of pepsin prepa- 

 ration. The scum is collected and preserved, and is either dried 

 and afterwards powdered, or it is mixed, whilst yet moist, with sugar 

 of milk. In both these forms it has been sold in commerce. 



Various very active preparations of pepsin have of late made 

 their way in commerce, as for instance, Jensen's 'Crystal Pepsin,' 

 Liebreich's ' Pepsin Essenz/ Benger's ' Liquor Pepticus,' and Bul- 

 lock's 'Acid Glycerin of Pepsin,' which last is a glycerin extract 

 of extraordinary and remarkably uniform strength, and possessing 

 scarcely any other taste than that of glycerin. 



Having described the various modes of obtaining pepsin and its 

 preparations, it is necessary to discuss the nature of the acid or acids 

 of the gastric juice, before undertaking the study of gastric diges- 

 tion, from which alone we can derive any satisfactory information as 

 to the properties of pepsin. 



SECT. 8. THE ACID (OR ACIDS) OF THE GASTRIC JUICE. 



It was pointed out in the historical account of the earlier re- 

 searches on digestion that many of the older writers supposed gastric 

 digestion to be due to the secretion of an acid corrosive fluid. 



The fact that the gastric juice was essentially an acid fluid was 

 not admitted until nearly the first quarter of the present century 

 had passed. It is true that some observers, as Carminati, Brugna- 

 telli, Viridet, Werner 1 , Montegre 2 , had experimentally determined 

 that in particular cases the gastric juice had an acid reaction, but 

 their observations were not' supported by those made by Spallanzani 

 and others 3 . Moreover certain of the evidence adduced in favour of 

 the acidity of the gastric juice was not sufficient, as we now know, 

 to prove the fact ; as for instance that milk is curdled by the secre- 

 tion of the stomach, a phenomenon now known to be independent 

 of an acid reaction. 



1 Carminati, Brugnatelli, Viridet, Werner, quoted by Tiedemann and Gmelin in 

 Die Verdauung nach Versuchen, Vol. i. p. 147. 



2 Montegre, Sur la Digestion de VHomme. Paris, 1804. 



3 See Magendie, Precis elementaire de Physiologic, T. 11. p. 11. 



