Temperature Limits of Life

Abstract

Homeotherms are substantially more capable of resisting cold than heat, if the normal rectal temperature is taken as the point of departure. With the possible exception of man, the number and effectiveness of the mechanisms protecting against loss of heat are also far greater. In contrast to the poikilotherms, whose temperature resistance can be essentially characterized by their lethal temperatures, a number of critical temperature ranges can be distinguished for homeotherms: 1. the external temperature at which the capacity for temperature regulation is exceeded and the core temperature changes; 2. the core temperature at which the regulatory centers are paralyzed and 3. the lethal temperature. Special conditions are also found, in which local temperature damage takes place while overall temperature regulation is maintained. Accordingly, the tolerance shown by homeotherms for extreme temperatures is determined by the interaction of a large number of factors.