By a study of the enzymes contained in fibrinous exudates produced by injection of a sterile inflammatory irritant (turpentine) conditions have been found in which each of two enzymes occurs alone. The one, leucoprotease, digests in the presence of alkali; the other, resembling lymphoprotease, digests in the presence of acid, yet both exhibit almost maximum activity in an approximately neutral medium. It is probable that both enzymes, in the body, exert their greatest activity in an approximately neutral medium, slight changes in reaction increasing digestion by the one, and suspending digestion by the other. The enzyme digesting in acid, present in the fibrinous exudate obtained after a single injection of turpentine, disappears when repeated injection of the same irritant transforms the sero-fibrinous into a purulent exudate, and causes accumulation of leucoprotease in great quantity.