The differentiation of true and pseudo cholinesterase by organophosphorus compounds.

1. Five preparations of testicular hyaluronidase, one of streptococcal and one of staphylococcal origin were compared by an accurate skin-diffuiion assay and by viscosimetric and turbidimetric methods. 2. With testicular preparations the results of the three methods agree well, provided that the potency is measured in terms ofa reference preparation of enzyme, and that the pH and ionic strength of the solvents are approximately physiological. It is desirable to use highly purified substrate, and to stabilize the enzymes with gelatin rather than gum acacia. 3. The activities of the two bacterial enzymes showed a close but not complete correlation between the three tests.