A series of test tube experiments was undertaken to determine the action of promin∗ and its parent substance, diamino-diphenyl sulfone, upon the tubercle bacillus, and to learn whether or not p-aminobenzoic acid would inhibit the effect of these compounds as it has been shown to inhibit the effect of sulfanilamide upon other organisms.

All these tests were made upon both virulent and avirulent mutants of the human strain H₃₇ used by Feldman, Hinshaw and Moses, 1 2 3 4 in their work on promin, and by writers in previous studies on sulfonamide drugs. The cultures were grown on Steenken and Smith's solid medium, or on Proskauer and Beck's fluid medium.

Promin in Steenken and Smith's Medium. Promin was added to tuves of this medium in concentrations from 1 to 80 mg% and the mixtures were then seeded with the 2 variants of the standard bacillus. Chart I demon-startes comparatively slight inhibitory action until concentration of 40 mg% is attained. The effect is more marked upon the avirulent (R_a) mutant.

Diamino-Diphenyl Sulfone† in Steenken and smith' Medium. The quantities of this drug used were based on the amount of the parent substance, diamino-diphenyl sulfone, which constitutes about one-third of the molecular weight of promin. Therefore the weights used in this test were in the ratio of one part of the diamino-diphenyl sulfone as compared to 3 parts of promin used in the previous test. These quantities varied from 0.3 to 26 mg% as shown in Chart II. These drug concentrations had much more effect upon the growth of the tubercle bacilli than the larger quantities by weight of promin. The additions of 1.6 mg% reduced growth to the same degree produced by 40 mg% of promin.