GENERAL ACTION OF ACIDS 327 



fauces and allay thirst. They further exert some astrin- 

 gent and antiseptic effects by precipitating a scum of 

 proteid on the mucous membrane. If not neutralised 

 before they reach the intestines, they increase especially the 

 pancreatic secretion, and to a less extent the bile. The 

 pancreas is stimulated to secrete by the absorption into the 

 blood stream of secretin. This substance is developed by 

 the action of acids on the duodenal mucous membrane, the 

 cells of which manufacture prosecretin, the antecedent of 

 secretin. Thus the pancreatic secretion is proportional to 

 the amount of acid leaving the stomach in the chyme, and 

 if this is naturally deficient, a mineral acid must be given 

 by the mouth. 

 Acids assist digestion in several ways. 



(1) They furnish the gastric juice with its acid con- 

 stituent, which, unlike the pepsin, is not capable of repro- 

 duction, and without which the digestive power of the 

 gastric solvent is impaired. Hydrochloric acid, being the 

 chief natural gastric acid, is generally prescribed when the 

 acidity of the gastric fluid is believed to be deficient, as it 

 sometimes is in young animals living chiefly on milk, in 

 febrile, enfeebled, or old subjects, or in those suffering from 

 gastric catarrh. To aid digestion, acids are given shortly 

 after food. Where there is want of appetite and irregular 

 action of the bowels, acids are given conjoined with 

 bitters. 



(2) Acids, by their astringent action, check gastric secre- 

 tion when this is excessive, as it appears to be in cases of 

 indigestion, where the fluids in the mouth are sour, not only 

 after, but before feeding, and where animals instinctively 

 lick the walls, or eat alkaline earthy matters. In such 

 cases the alkaline treatment frequently adopted affords 

 temporary relief ; but a laxative, followed by acids, gener- 

 ally removes the conditions on which the dyspepsia depends. 

 To such patients acids are given before feeding, and a pro- 

 tective film of albumin is deposited on the mucous membrane 

 so that useless secretion is arrested. 



(3) Acids acting antiseptically check fermentation, and 

 thus prevent formation of gases and irritating organic acids. 

 This is an important use of the hydrochloric acid normally 



