The disturbance of fluid balance following extensive cutaneous burns is a well known phenomenon. Even though the fluid intake is relatively great during the first twenty-four hours, there is a marked urinary suppression. The normal ratio between fluid intake and output usually does not become established before the end of from forty-eight to seventy-two hours. During this period, the urine is deeply colored, has a high specific gravity, and may contain a trace of albumin. In view of this apparent suppression of the renal function and the fact that sodium chloride is badly tolerated by kidneys showing irritative lesions, it seemed desirable to study the sodium chloride metabolism and its relation to protein metabolism. A number of observers have investigated the nitrogen metabolism in extensive burns. Robertson and Boyd1 found that the nonprotein nitrogen of the blood was increased from 40 to 50 per cent in rabbits following burns.