214 THE GASTRIC JUICE. 



Many different opinions have been entertained as to the 

 acids of the gastric juice. Vauquelin maintained the exis- 

 tence of phosphoric acid, Tiedemann and Gmelin of hydro- 

 chloric acid; Chevreul, Leuret, and Lassaigne, and more 

 recently, Bernard and Barreswil, of free lactic acid, while 

 Blondlot has strenuously maintained that the acidity of the 

 gastric juice is due to acid phosphate of lime. 



The experiments of Mr Bernard have undoubtedly gone 

 far to prove the existence of free lactic acid in the stomach, 

 and to disprove the presence of free hydrochloric acid; still 

 the matter must be looked upon as far from settled. 



The remarkable animal substance called pepsine, which we 

 have mentioned as one of the constituents of gastric juice, is 

 found besides in the mucus and coats of the stomach. It 

 is conveniently prepared by macerating the coats of the 

 stomach, first in water gently heated (between 80 and 

 1 00), and then in cold water. On alcohol being added to 

 the latter, a floculent precipitate of pepsine falls, which is 

 soluble in cold water, and possesses most remarkable diges- 

 tive properties. It is not prone to decompose, and 1 part 

 in 60,000 parts of water will dissolve albuminoid sub- 

 stances, the action being increased on the addition of a 

 few drops of dilute hydrochloric acid. This substance 

 reddens litmus, and in its ultimate composition approaches 

 the protein compounds, from which it differs in con- 

 taining more nitrogen.* The salts of the gastric juice 

 are chiefly chloride of sodium, potassium, and magnesium. 

 Phosphate of lime is present in small quantities, and alkaline 

 sulphates are absent. There are other saline ingredients 

 which are only occasionally found. 



If we now take into consideration which of the constitu- 



* See BRINTON On Food and its Digestion, page 121. 



