1911 Encyclopædia Britannica/Pepsin

PEPSIN, an enzyme or ferment obtained by drying the mucous lining of the fresh and healthy stomach of a pig, sheep or calf. As used in medicine it consists of a light yellow-brown or white powder or of pale yellow translucent grains or scales. It is only slightly soluble in water and alcohol. Pepsin is used to help gastric digestion in old people and in those in whom there is a deficient secretion of the gastric juice. It is useful in chronic catarrhal conditions of the stomach, the dyspepsia of alcoholism, and in gastric ulcer and cancer of the stomach.

Pepsin digests the albumens but is useless in the digestion of fats or carbohydrates. It may also be used to predigest albuminous foods. The following is a method of peptonizing beef. Take 1/4 ℔ of minced raw lean beef, 1/2 pint of water containing 0·2% of hydrochloric acid, place in a jar with 30 grs. of pepsin, set in a warm place at 110° F. for 3 hours, stirring occasionally. Then quickly boil it. It is usually unnecessary to strain it, as the meat is reduced to a fine almost impalpable powder which is readily assimilated. Many varieties of proprietary peptonizing tablets are on the market and are convenient for the preparation of peptonized milk. The following is a method of preparing it. Take a clean glass quart bottle, pour in a pint of perfectly fresh cold milk, then add a teacupful of cold water in which a peptonizing tablet has been dissolved. Submerge the bottle in a can of water at 100° F. for from 5 to 10 minutes, take out the bottle and place on ice to prevent the further action of the pepsin. If no ice is convenient bring the milk to a boil for the same purpose. If the action of the pepsin be continued for a much longer period the milk becomes bitter to the taste from the development of excess of peptones. Predigested foods should not be used over a long period or the digestive functions of the stomach may atrophy from disuse.

Pancreatic solution, derived from the pancreas of a pig digested in alcohol, has the power of converting starch into sugar, and albumen and fibrin into peptones. It only acts in an alkaline medium and at a temperature under 140° F. If used to peptonize milk sodium bicarbonate should be added. Many commercial preparations are on the market. Trypsin, the principal ferment of the pancreas, also changes proteids into peptones.