Since Lewis (6) discovered the vascular &dquo;hunting reaction&dquo;, many studies have been performed to elucidate the mechanisms involved and the occurrence of this response in various normal and abnormal states. Krog, et al. (5) indicated that the hunting reaction was much more effective in determining the local resistance to cold compared to other measurements of blood flow. Yoshimura and Iida (10) utilized this reaction to evaluate the racial differences between cold habituated Chinese and Mongolians, and non-habituated Japanese. Meehan (7) compared the hunting reaction of Caucasian, Negro, and Alaskan natives. Elsner, et al. (1) reported that vasodilation occurred earlier and with a greater magnitude of change in arctic Indians in contrast to a control group.Few studies, however, have attempted to compare the differences in this response between ethnic groups who are not cold habituated. The present study was conducted to determine any significant racial difference between Caucasian and Japanese in order to probe the quality and degree of human adaptability to cold in both groups. METHODSLocal cold immersion tests were conducted on nine male Caucasians, age 21-27, and eight male Japanese, age 20-32, who had lived in California from 2 to 18 months. The subjects were seated comfortably, wearing light clothes, in a quiet and pleasant room having an ambient temperature of 22 -!-1 C for one hour before the experiment. Subjects participated in four experiments being subjected to a different cold water temperature each time with at least two days elapsing between tests. The cold water bath temperatures were 0, 5, 10, and 15 -!-1 C. Copper-constantan thermocouples were placed on both middle fingers and right thumb with adhesive tape. These skin temperatures were recorded continuously by means of a Honeywell temperature recording system to an accuracy of 0.1 C. The pulse volume, strain gauge plethysmograph, was recorded simultaneously from the left index finger as an indication of vasodilation or vasoconstriction concurrent with changing skin temperatures. The strain gauge output was recorded following appropriate amplification on a Sanborn twin-channel recorder. Control observations, in air, were made for a period of five minutes after which the at UNIVERSITE DE MONTREAL on August 13, 2015 ang.sagepub.com Downloaded from

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