A Characteristic of Human Temperature Regulation. ∗

Abstract

The temperature regulatory mechanism maintains rectal temperature of non-basal men sitting at rest in a comfortable environment slightly above 37°C. In certain cold environments which cause shivering, rectal temperature declines to about 35 or 36°C where it tends to become stabilized. This was observed in experiments in which subjects sat immersed to the neck line in well-stirred water baths maintained at 20, 25, or 30°C. (Table I). Rectal temperatures were obtained with thermocouples placed 10 or 15 cm within the rectum. Gastric temperatures taken toward the end of experiments by means of thermocouples inserted in modified Levine tubes were somewhat higher (about 36°C) than rectal temperatures (Table II). Temperatures taken within the stomach are possibly a more reliable index of deep body temperature under the conditions of these experiments than measurements made within the rectum, because the close proximity of surrounding cold water to the junction of the rectal thermocouple may cause falsely low readings.

The fact that deep body temperature became stabilized at approximately the same temperature in all experiments, even though the intensity of shivering necessary to produce sufficient metabolic heat to maintain this temperature varied considerably (Table III), shows that 36°C is a critical temperature at which the thermoregulatory mechanism initiates or attempts to initiate shivering of adequate intensity to prevent further body cooling under these experimental conditions. As might be expected, shivering did not reach its greatest intensity in the experiments until body temperature level (Table III). Evidence that 36°C is a temperature in some way important to human thermoregulation has been obtained by others. For example, the results obtained by Burton and Bazett 1 in experiments in which subjects were immersed in relatively warm water showed that metabolic heat production increased above basal level as rectal temperature approached 36°C.