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Six volunteers raised their rectal temperatures to 104℉ by 40–50 minutes' work at 93℉ wet-bulb temperature. The rates of fall in rectal temperatures were studied during cooling by six different methods. The most rapid method of cooling occurred when subjects sat at rest in an air condition of 90℉ dry bulb and 87℉ wet bulb and evaporative cooling was accelerated by wetting the body surface continuously for 1 hour; no significant difference in cooling was observed between airflows of 120 ft/min. and a jet of compressed air held 1–3 ft from subjects. Merely seating individuals in air conditions of 70℉ with 20% relative humidity in still air was almost as effective. Immersion in cold water and sitting in air conditions of 90℉ (D.B.) and 87℉ (W.B.) without aiding evaporative cooling are significantly less effective than the foregoing methods. Resting subjects at 97℉ (D.B.), 93℉ (W.B.) and 120 ft/min. air velocity results in very slow cooling. ‘Afterdrop’ in rectal temperature after ice-cold water cooling may be associated with severe circulatory shock. Oral temperatures are a less reliable index of core temperature than rectal. Submitted on February 16, 1959

No abstract

Four trained young men, worked for 4 h/day at 43-50% of their maximum aerobic capacity for 3 days at 25 degrees C db, 18 degrees C wb and then for 10 consecutive days at 45 degrees C db, 32 degrees C wb. Their thermal status was assessed using direct calorimetry. As a group, the men showed classical acclimization responses, but there were marked individual differences. The calorimetric analysis revealed that reductions in strain were associated with minor changes in heat balance confined to the first and last hours of exposure. Events occurring within the first 4 days appeared to have little effect on body temperatures. Significant decreases in body temperature took place only when sweat and evaporation rate increased. A 10% increase in evaporation rate was accompanied by a 30% increase in sweat rate and a 200% increase in unevaporated sweat; thus, there is a wasteful overproduction of sweat. By the 10th day skin temperature was confined to the level necessary to evaporate sufficient sweat to achieve thermal balance with a fully wet body surface. The efficiency of heat transport within the body did not change with acclimatization.

Using data from an ongoing mark–resight program at Marion Island, we tested whether there is variation in the timing of the breeding haulout of female southern elephant seals, in relation to breeding experience. Females were classed as primiparous or multiparous according to their age and known life histories. The mean breeding season haulout date of primiparae was found to be significantly earlier than that of multiparae in nearly every year of the study. This was caused by differences in the timing of arrival, not by differences in the duration of tenure. In addition, in consecutive seasons, mean moulting and breeding haulout dates of individual females were shown to be significantly correlated. The results of our study fit well with our expectations, assuming that the nutritional condition at the time of the sensitive photoperiod phase affects the timing of implantation, because females in their first pregnancy generally moult sooner than post-parturient females and are likely to recover depleted reserves earlier.