Abstract
1. In tetrazolium stains for the succinic dehydrogenase system, diphosphopyridine nucleotide diaphorase and triphosphopyridine nucleotide diaphorase, the rate of staining can he greatly increased by adding any one of a number of soluble oxidation-reduction indicators to the incubation medium. The characteristic staining patterns are not altered.
2. This modification of tetrazolium staining interposes a dye as a carrier between the enzyme and the tetrazolium salt and makes it possible to stain for enzymes which do not react directly with tetrazolium.