We have studied the vitamin C content of the adrenals of laboratory animals injected with bacterial toxins, or viruses, or dying from spontaneous infections, using a silver nitrate solution or the indicator 2:6 dichlorophenol-indophenol (technique of Birch, Harris and Ray). By this latter method, we have also examined the tissues of guinea pigs apparently completely recovered from sublethal injections of diphtheria or tetanus toxins and fed excess vitamin C. Determination by silver nitrate. Having found the adrenals of guinea pigs dying of diphtheria toxin did not reduce silver nitrate, while those of the control animals were rapidly blackened, we applied this method to the adrenals of animals fed a complete diet showing various pathological conditions with the following results. A positive reaction was found in rabies-fixed virus (4 rabbits); in infection with human tubercle bacilli of moderate virulence (3 guinea pigs), killed 2 months after inoculation, showing slight lesions; and after injections of toxin of dysentery of dysentery bacilli (3 rabbits) dead in 18 to 48 hours. A diminution, more or less marked, of the reducing power of the adrenals, especially the cortex, occurred after a lethal injection of tetanus toxin (5 guinea pigs); of dysentery toxin (4 mice, dying in 3 to 5 days); in mouse typhoid (4 mice infected per os and dying in 4 to 6 days); and after repeated injections of histamine-hydrochloride (4 guinea pigs and 3 mice). In yellow fever the reactions gave irregular results in mice dying after intracerebral inoculations. In one case rapid blackening occurred; in 2 others the reaction was incomplete. Determination by 2,6-dichlorophenolindophenol titrations. By this method the tissues of supposedly normal guinea pigs (200–300 gm.) were examined. These animals were bought in the open market and their previous diet was unknown. The ascorbic acid content of their organs varied greatly. The figures are given in mg. per gm., adrenals 0.27–0.66, liver, 0.05–0.12. Variations were also noted in the tissues of guinea pigs fed carrots, hay and oats for 10 days, adrenals 0.15–0.30, liver 0.02–0.04.