Prep. One process of preparing pepsin is to wash the stomach, scrape off the mucous membrane, and digest it in distilled water; filter and add acetate of lead, which throws down a precipitate of pepsin with the metal. This precipitate is afterwards submitted to the action of sulphuretted hydrogen, which combines with the lead and leaves the pepsin in solution. After acidification with lactic acid, the solution is evaporated until a gummy mass is left, which is then mixed with dry starch. The pepsin from the pig's stomach, first proposed by Dr. Beale, is made by Mr. Bullock without the employment of the lead process.

Description. The pepsin prepared from the calf's stomach and mixed with starch (Boudault), occurs in a grayish-white powder, having an acid and often disagreeable odour. Pepsina porci (Bullock) is somewhat more coloured, free from acid, and with an odour closely resembling baked flour.

Prop. & Comp. Pepsin (independently of contained starch) is soluble in water; the solution is precipitated by salts of lead and mercury, likewise by tannic acid and alcohol. A solution of pepsin in water, when acidulated with lactic, phosphoric, or hydrochloric acids, has the power of causing the solution of fibrin or albumen when kept at the temperature of the body (100° Fah.); and the amount of fibrin or albumen dissolved by a given weight of the pepsin may be taken as an indication of the value of the medicine. A temperature above 120° Fah. injures or destroys the solvent powers of pepsin.

Pepsin is a protein body, but little else is known as to its composition; it appears to possess what are termed catalytic powers.

Therapeutics. Pepsin has been given largely in cases of dyspepsia, especially of the atonic kind, and is asserted to have proved a very valuable remedy. Its beneficial action is somewhat difficult to explain, seeing that the ordinary doses of the drug are able to cause the solution of so small an amount of nitrogenized matters when out of the body, fifteen grains of Boudault's pepsin dissolving but sixty grains of dried fibrin.

Dose. Of pepsin (Boudault), about 15 gr. to 20 gr., given with a meal; of pepsina porci, 2 gr. to 4 gr.

It is stated that the latter pepsin is five times stronger than the former.