218 THE PRINCIPLES OF AGRICULTURE 



The addition of such elements to the food 

 should be made later and a little at a time. 



3c. The gastric juice 



386. The stomach produces three digestive 

 principles, which may be separately considered : 

 muriatic or hydrochloric acid, pepsin, the milk- 

 curdling ferment. These materials comprise the 

 gastric juice. 



387. Free muriatic acid is strongly antiseptic, 

 especially checking such fermentations as occur 

 in the alkaline or neutral saliva, in the first three 

 stomachs of ruminants or in the crop of the 

 bird. This exposure of the food successively to 

 alkaline saliva and acid gastric juice kills off 

 myriads of bacterial ferments which would other- 

 wise reach the intestine, to prove irritant or 

 poisonous. Many still pass into the intestine in 

 masses of undigested food, or because they can 

 survive both alkaline and acid solutions, or 

 because they have passed into the condition of 

 spore, which, like the dried seed of plants, is 

 comparatively indestructible. 



388. The muriatic acid further softens, disin- 

 tegrates, and dissolves the various nitrogenous 

 food principles (coagulated albumin, fibrin, gela- 

 tin, casein and vegetable gluten). 



389. Pepsin is a ferment which is secreted in 



