With the purpose to elucidate the cause of the increase in substances positive to Donaggio reaction of urine in fatigue the author administered adrenalin chloride (diluted 1, 000-fold), ammon chloride and ACTH to rabbits and induced conditions simulating those irregularities of the body in fatigue. In the observation of their urine the following results were obtained. 1. In the rabbit administered adrenalin chloride the urine Donaggio value reaches its maximum 2-3 hours after the injection and thereafter descending gradually, it returns to normal lever 24 hours afterwards. The amount of urine likewise increases 2-3 hours after the injection, but urine pH does not show any alteration. 2. In the rabbit given oral administration of ammon chloride the urine Donaggio value reaches the maximum six hours after the administration and decreasing gradually thereafter, it returns to normal level after 24 hours. The amount of urine likewise increases 2-6 hours after the administration, substantiating the increase in the content of substance positive to the urine Donaggio reaction being excreted hourly. Urine pH shows the minimum 3-6 hours after the administration. 3. In the rabbit administered ACTH the urine Donaggio value, increasing markedly already one hour after the injection, reaches the maximum value after three hours. Thereafter decreasing rapidly, it returns to normal level after 24 hours. No changes can be recognized in the urine content and pH. 4. In the rabbit not treated with drug the maximum variation in the urine Donaggio value ranges within two, and no marked change can be recognized in the urine content and in pH. 5. In drawing the correlation curve between the urine Donaggio value and the concentration of remnant methylene blue the result obtained aproximately coincides with that reported by Nakayama. Calculating from this curve, the Donaggio vaules can be correctly determined within the limit of error of 1.0±0.1.