THE NATURE OF SERUM ANTITRYPSIN : STUDIES ON FERMENT ACTION. XIII.

1. The ferment-inhibiting action of the serum is due to the presence of compounds of the unsaturated fatty acids. 2. These fatty acid compounds may be removed from the serum by means of chloroform or ether. 3. Soaps prepared by saponifying the chloroform or ether extracts inhibit the action of trypsin. 4. The anti-enzyme action of the serum can be removed by filtering acid serum through kaolin, and can in part be restored by extracting the kaolin. 5. The decrease in strength of anti-enzyme in old sera is probably due to the action of the serum lipase. 6. Iodin, potassium iodide, or hydrogen peroxide remove the inhibiting action of the serum. 7. Soaps of the unsaturated fatty acids lose their ferment-inhibiting action when heated with serum at 70° C.