5, MEDIAN LETHAL DOSAGE OF NUCLEAR RADIAT LON a. The median lethal dosage (MLD) of nuclear radiation was obtained suc- cessfully for mice, dogs and swine. mortality is to be expected. The MLD is defined as that dosage at which 50% On EASY shot, i.,'720 mice were exposed in 29 cylinder were recovered alive stations at distances ranging from 1,000 to 1,750 yards and all on BE day, 6 hours after the detonation, The mortality rate over a period of 28 days ned, was determined and a smooth curve relating dosage to mortality was obtai THe MLD occurred at the station which was 1,416 yards from ground zero. b. On EASY shot, 19 swine were placed in cach of nine stations at distan~ ces ranging from 1,300 to 1,750 yards, was determined, The mortality rate over a period of 30 days On the 30th day after the shot there were two swine living fromthe station at 1,650 yards and cight living from the station at 1,750 yards. The MLD, therefore, occurred at some distance between 1,650 yards and 1,750 yards from ground Zero. c. On EASY shot, 10 dogs were placed in each of ninc stations at the same distance as the swine. “the mortality rate was determined over a 30 day period, on E plus 30 days there were 2 dogs living from the station at 1,620 yards, 5 living from the station at 1,650 yards and 9 living from the station at 1,750 yards from The MLD, therefore, occurred at about 1,650 yards. ground zero, d, The best data were those for mice, from which a smooth dosage mortality curve can be drawn. ‘The observed MLD based on the theoretical gamma radiation yield for the EASY weapon was lower by a factor of approximately 0.7 than the MLD of mice of the same strain exposed to supervoltage X-ray. The MLD for dogs based on the theoretical gamma radiation was approximately the same as that obtained with super- voltage X-ray. When the MLD was based on measurement of film packs placed within the containers in which the dogs were exposed, a somewhat Lower value was obtained. The MLD for swine, based on the theoretical ganma radiation, was conspicuously lower than the value obtained with supervoltage X-ray. Tentatively, this discrepancy is attributed to the hot, humid environment, which was tolerated poorly by the swine, It appears that for future ficld tests, dogs arc more satisfactory than swine for the determination of MLD and for the study of therapy on the MLD, Results obtained from the radiation depth dosage (discussed later) offered some explanation for the . discrepancies noted in determining the median lethal dosages of the animals. 6, THERMAL RADIATION INJURY @. On EASY shot, 46 swine and 16 dogs were anesthetized and placod in six ee