Cold Acclimatization in Eskimo

0 N EXPOSURE to cold the body has a complicated physiological problem to solve. There is a limit to the heat it can produce to provide for an increased heat loss and during exposure of much severity a heat deficit is incurred. While peripheral tissues are cooling, the central body temperature must be kept within a very narrow range if the function of vital organs is to be maintained. If the accomplishment of this results in the failure to maintain a certain delivery of heat to the limbs, the usefulness of hands and feet is impaired. On the other hand if circulation to the extremities and to the surface of the trunk is greater than that required for necessary function, the heat loss is needlessly large and central body temperature is prejudiced. There is obviously room for subtle adjustment if vital needs are to be met and working capacity reasonably maintained in an economic fashion. It is the sum of the adjustments following repeated or prolonged exposure to cold which constitutes acclimatization to cold. There has been doubt that acclimatization to cold exists in man. Many early experiments in the laboratory supported the view that it does not occur while observations in the field suggested that it does. The literature as a result is confusing. This is not surprising for the search for acclimatization had to begin before the nature of it was known. Often evidence was looked for in subjects thought to be acclimatized who actually were not. Another dficulty has been the selection of proper tests. The basis so f a r of all tests of acclimatization is a defined cold exposure and the observation of one or more physiological parameters. If the exposure is too severe, the test may be so indelicate that a real difference between subjects may not be apparent. Also, there has often been failure to recognize that there is in some respects a phasic response to continued exposure to cold. For instance, the blood volume is first reduced and then increased. It is, therefore, impossible to speak simply of the effects of cold. It is necessary to speak of the effects of one set of environmental conditions, temperature, air movement, humidity, and radiation, on subjects whose clothing is described and whose previous cold exposure is defined. At a time when no physiological definition of acclimatization was available and it was not known how much exposure was required to achieve acclimatization, an attempt was made to get around the difficulty of finding fully