Origin. - A proteolytic ferment or enzyme obtained from the glandular layer of fresh stomach of the hog Sus scrofa, and capable of digesting not less than 3000 times its own weight of freshly coagulated and disintegrated egg albumin when tested by the process given in the United States Pharmacopoeia.

Description and Properties. - A fine white, or yellowish-white, amorphous powder, or thin, pale-yellow, or yellowish, transparent or translucent grains or scales, free from offensive odor, and having a mildly acidulous or slightly saline taste, usually followed by a suggestion of bitterness. It slowly attracts moisture when exposed to the air. Soluble, or for the most part soluble, in about 50 parts of water, with more or less opalescence; more soluble in water acidulated with hydrochloric acid; insoluble in alcohol, ether, or chloroform. Pepsin usually has a slightly acid reaction. It may be neutral, but should never be alkaline.

Dose. - 5-60 grains (0.3-40 Gm.) [4 grains (0.25 Gm.), U. S. P.].

Antagonists and Incompatibles. - Tannic and gallic acids are incompatibles. Mineral salts, alcohol more than 10 per cent., and alkalies precipitate pepsin from solution, the latter two impairing its digestive property.

Synergists. - Diluted hydrochloric acid, in not over 2/10 of 1 per cent., increases its digestive action.

Physiological Action. - Its only influence seems to be upon the digestive system. Pepsin is a typical restorative, being a normal constituent of the gastric juice, and in the presence of hydrochloric acid digesting the proteid elements of the food, converting them into albumoses, and finally into peptones.

Therapeutics. - Externally and Locally. - Its digestive action is utilized to dissolve or digest the false membrane in diphtheria and croup. A solution of pepsin has also been injected into the bladder to digest blood-clots.

Internally. - As a restorative, where there is a lessened secretion of gastric juice, atonic dyspepsia, apepsia of infants, cancer of the stomach, and gastric ulcer, pepsin has proved serviceable. It is also employed to favor digestion in convalescence from acute and long illness. It is frequently necessary to give pepsin, or "peptonized milk." in acute dyspeptic diarrhea of infants.

Administration. - Pepsin should be given in powder or dissolved in glycerin (glycerol of pepsin), or in water acidulated with hydrochloric acid, directly after meals.

The drug should not be given continuously for too long a period, lest the function of the stomach become impaired from disuse, the artificial digestion having replaced the natural, normal process.

Unless there be some direct indication for its use, rather than give pepsin it is better to stimulate the gastric glands to secrete a larger amount of their normal juice, that they may not lie idle, and their function be consequently impaired by disuse. Hydrochloric acid administered with pepsin probably promotes glandular activity slightly. Often, however, pepsin must be given, and in certain patients the stomach is in such a condition that nutrient en-emats must be administered. Yet, since the rectum possesses very feeble powers of digestion, foods should always be predigested. Suppositories of peptonized meat are frequently used for this purpose.