The serum of an inflammatory exudate has the power of inhibiting the action of proteolytic ferments contained in the leucocytes. This anti-enzymotic power is possessed by the blood serum from which it doubtless passes into the exudate. In the later stages of inflammation there is some diminution of this anti-enzymotic action. The anti-body contained in the serum is destroyed by a temperature of 75° C. The proteolytic ferments of the leucocytes act both in an acid and in an alkaline medium but are most efficient in the latter. The anti-enzymotic action of the serum is favored by an alkaline reaction, but is completely lost in an acid medium.