ACTION OF ACIDS 305 



chloric, 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 constricting 

 tissues, and also hemostatics in causing compression of blood vessels by 

 contracting the tissues about them. Nitric acid is commonly 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 appro- 

 priate than other agents in most cases, on account of their irritant action. 

 Free hydrochloric acid as it exists in the gastric j-uice (0.2-0.3 of 1 per 

 cent.) is a powerful antiseptic and even germicide. 



Action Internal. — Alimentary Canal. — The classical experiments of 

 Pawlow have materially altered our conceptions of the action of acids. 

 We have shown (p. 19) that indirectly, by stimulating the formation of 

 secretin in the stomach and intestines, they excite the activity of all the 

 glands giving rise to the secretions concerned with digestive activity. 

 They all aid digestion. Hydrochloric acid is particularly serviceable in 

 gastric anacidity, being the natural acid of the gastric juice. The mineral 

 acids also possess a certain degree of antiseptic action on the contents 

 of the digestive tract. Diluted acids are called refrigerants in imparting 

 a sense of coolness to the skin and mucous membrane of the mouth, and, 

 by augmenting the secretion of saliva, relieve thirst in fever. The acids 

 exert a local stimulant and astringent action upon the intestinal canal. 

 Nitric acid is particularly a stimulant, sulphuric acid an astringent. 



Constitutional Action. — Almost all living matter possesses an alka- 

 line or neutral reaction. An animal dies from acid poisoning even before 

 its blood becomes neutral. The constitutional action of acids is seen after 

 absorption of dilute solutions. Acids are immediately converted into 

 salts — as acid can not exist as such in the tissues or blood. In the case 

 of herbivora the fixed alkalies of the tissues and blood thus neutralize 

 acid as it is absorbed. When the alkalies of the blood and tissues are 

 consumed the animal dies. Herbivora are very susceptible to acid poi- 

 soning, as in*them the lessened alkalinity of the blood renders it unable 

 to carry carbonic acid from the tissues to the lungs. 



Carnivora are more resistant to acid poisoning because they possess 

 a protective power whereby they are able to liberate free ammonia from 

 their tissues and thus neutralize absorbed acid and save — to a consider- 

 able extent — ^the fixed alkalies in their blood and tissues. 



The symptoms of acute acidosis include: dyspnea, twitching, con- 

 vulsions, coma, depression of the heart and vaso-constrictor centres, 

 collapse and death by asphyxia and respiratory failure before the blood 

 becomes even neutral. There is diminished carbon dioxide content in the 

 blood explaining the peculiar dyspnea, gasping for breath, and later 

 short, shallow, feeble breathing. The acid-neutralizing power of the 



Digitized by Microsoft® 



