PHYSIOLOGICAL EFFECTS OF CONTINUED COLD ON ANIMALS AND MAN*

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Abstract
The acclimation of small animals to constant cold, which approximately doubles heat production, generally leads to development of increased cold resistance through an increased capacity to produce heat. The resulting metabolic alterations are the principal focus of studies on cold acclimation today. The process is calorigenically expensive and perhaps does not lead to a lasting improvement in tolerance to cold. A much greater economy of energy is seen in animals acclimatizing to cold climates in which development of increased fur insulation and insulative cooling of peripheral tissues lead to heat conservation. These processes may be combined with the metabolic type of change seen in cold-conditioned animals. Metabolic alterations comparable with those in cold-conditioned animals have never been observed in man, but the extent and duration of exposure to cold have not been comparable. Field studies have suggested reduction in "core" and greater heating of appendages, coupled with delayed metabolic response. In studies on man, the 2 opposing adjustments, peripheral heating (as seen in Eskimos, Indians, cold-acclimatized Caucasians) and toleration of greater peripheral cooling (as seen in Australian Aborigines and Alaskan students) are also seen as natural climatic responses. The racial differences may be partly inherited, partly acquired. From the limited data it appears that the extent of protection of the whole body from cold has an important bearing on the type of peripheral adjustment observed.
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