Richet,1 in his monograph on animal heat, tabulated 109 examples of hyperthermia in man with temperatures ranging from 42 to 44.6 C. (107.6 to 112.2 F.). There were 13 survivals in this group. He rejected as unreliable several reported observations of temperatures from 44.1 to 50 C. with recovery and expressed unwillingness to accept as valid any observation of temperature above 46 C. (114.8 F.). This decision was based not merely on clinical studies but on extensive physiologic experimentation and observations on various mammals. Hombourger2 defined fever as a morbid state resulting from exaggeration of proteolysis and disturbance of the heat-regulating mechanism, and he designated as hyperthermia a high elevation of temperature, whatever the cause. A fever with a temperature above 41 C. (105.8 F.) he designated as "hyperthermic fever." This author expressed agreement with Richet. He mentioned the famous cases of Jacobi and of Heber Jones, as