1. Normal serum protease is not specific; it is active in both dilute acid as well as alkaline media. It is destroyed by heating to 70° C. for thirty minutes. It is markedly impaired when heated at 56° C. for thirty minutes. It is inhibited by the unsaturated soaps and lipoids.
2. Guinea pig and rabbit serum contain relatively much protease; the leucocytes are without proteolytic ferments.
3. Normal human and dog serum contain little or no protease; the leucocytes are strongly proteolytic.
4. Serum complement and protease are not identical.
5. During various pathological conditions the non-specific protease is increased in both human and dog serum.
6. An increase in antiferment is in many instances coincident.
7. During the Abderhalden reaction the placental tissue becomes more resistant to enzyme action, because of the adsorption of the antiferment from the serum.
8. The dialyzed serum loses antiferment because of adsorption by the placental tissue or other adsorbing substances, including probably the dialyzing membrane.
9. The digestive substrate is the serum protein made available for protease action by the adsorption of the antiferment.
10. The proteases in pathological conditions investigated by us (pregnancy, tuberculosis, and pneumonia) are non-specific.