No abstract

No abstract

SUMMARY1. Six healthy humans were immersed sequentially in baths maintained at a steady temperature of either 28 + 1 or 38-8 + 1°C.2. Metabolic heat production was calculated by respiratory gas analysis. A ventilated capsule was placed on the forehead and sweat secretion was calculated from psychrometric recordings. Convective heat loss from one hand to a water-perfused glove provided a continuous measurement of vasomotor response.3. Heat production, sweating, and vasomotor heat loss were proportional to core temperature.4. Sweating and vasomotor response were parallel. Vasoconstriction was complete, before the onset of shivering.5. The thresholds for heat loss and heat production were superimposed, without a 'dead band' core temperature.

SUMMARY1. Four human subjects were rendered hyperthermic and hypothermic by immersion in warm and cool water, at 02.00, 08.00, 14.00 and 20.00 hr. Bath and oesophageal temperatures and pulse rate were recorded. Temperature preference was determined by operant behaviour and vote. The core temperature set-point for behavioural thermoregulation was estimated from the behavioural results.2. The results are in accord with those of previous studies of the nyethemeral cycling of autonomic responsiveness to heat and cold with a heating up phase before noon and a cooling down phase during the early night.3. Subjective sensations and behavioural responses were also found to follow a nycthemeral cycle with a minimum before noon and a maximum at 20.00 hr.4. The core temperature set point was 0.70 C higher after noon than before noon with a small phase advance from resting core temperature. This result suggests that the nycthemeral cyclic change in body temperature is due to a nyethemeral cyclic change in the set-point near to which body temperature is kept by both autonomic and behavioural thermoregulatory responses.

SUMMARY1. Four subjects were immersed in a stirred water-bath maintained at either 30 or 400 C. The left hand was placed out of the bath in a glove receiving water at a temperature selected by the subject as most pleasurable. Experiments were conducted during the euthermic state and during either spontaneous or induced fever.2. The results of control experiments confirm a previous observation using the same method, that preferred hand skin temperature was a linear function of internal temperature but also indicated an influence by mean skin temperature.3. The general pattern of response during fever was identical to that when fever was absent except that the regulated steady state internal temperature was higher and the slopes of preferred temperature plotted against internal temperature were steeper.4. The results seem to support the concept of a change in set point rather than that of a change in the gain of the thermoregulatory processes during fever.