252 INORG-iNIC AGENTS 



the other mineral salts. Nitric acid is less caustic, and 

 hydrochloric acid is the least corrosive. Nitric acid stains 

 the parts yellow, and hydrochloric, white. The vegetable 

 acids, as citric and tartaric acids, are slightly caustic, but 

 are irritant to the skin, and still more so to raw surfaces and 

 mucous membranes. An ounce of tartaric acid has caused 

 death in man through its local effect. The action of the 

 caustic alkalies is more widespread than that of the mineral 

 acids. Diluted sulphuric and nitric acids are astringents, 

 because of their power of condensing tissues, and also 

 hemostatics in causing compression of blood vessels by 

 contraction of the tissues about them. Nitric acid is com- 

 monly employed externally, because its effect is limited by 

 its own eschar, which is not dissolved by an excess of acid. 



Hydrochloric acid has no astringent effect and is not 

 used externally for its caustic properties. The acids are 

 antiseptic, but are less appropriate than other agents in 

 most cases, on account of their irritant action. 



Action Interned. — Alimentary Canal. — Acids stimulate 

 the normal alkaline secretions in the body, particularly 

 those entering the mouth and intestines. The flow of 

 saliva, bile and intestinal juices is therefore increased. 

 Diluted acids are called refrigerants in imparting a sense 

 of coolness to the skin aud mucous membrane of the 

 mouth, and, by augmenting the secretion of saliva, relieve 

 thirst in fever. In opposition to the action of acids in 

 stimulating alkaline secretions, exists the 'fact of their 

 checking acid secretions, such as the gastric juice and 

 sweat, and if the administration of acids is prolonged for 

 several weeks, gastric digestion may be impaired in conse- 

 quence, unless the gastric juice is abnormally deficient. The 

 acids exert a local stimulant and astringent action upon the 

 intestinal canal. Nitric acid is particularly a stimulant, 

 sulphuric acid an astringent, while nitric and nitrohydro- 

 chloric acids are especially cholagogues. Hydrochloric acid 

 assists digestion in supplying a deficiency in the normal 

 hydrochloric acid of the gastric juice, in aiding the conver- 



