STUDIES ON THE REACTIVITY OF SKIN VESSELS TO EXTREME COLD

PART1. A POINT TEST ON THE RESISTANCE AGAINST FROST BITE

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1. There were found marked individual differences in the vascular reaction to cold reported by Lewis which protects the temperature fall of fingers or toes in severe cold. The difference should be an essential factor in constitutional difference of resistance against frost damage.
2. A method was devised to determine the temperature reaction to cold by dipping the middle finger of the subject in ice water for 30 minutes, and measuring its skin temperature, and to compare the reactivity of the subject with one another by evaluating the so-called. “resistance index of frost bite” from the temperature curve thus determined. The method was called “a point test of the resistance against frost bite”.
3. The resistance index estimated by the method was fairly reproducible, as far as the experimental conditions were constant. When measuring repeated attempts should, however, be avoided unless after several hours, and to have such living conditions before and during the measurement that do not cause changes in the thermoregulatory function.
4. A marked seasonal change was found in the temperature reaction of one and the same subject, which increased in summer, and decreased in winter. The change was found to be mainly due to the change of room temperature. Even at the same room temperature, however, the reaction differed a little in summer and winter, i. e. is accelerated in the former when compared with the latter. The difference is probably due to an acclimatization of the vasomotor centre, in which the tonus changes to dilation of the skin vessels of extremities in summer, and constriction in winter.
5. Influences of environmental temperature were examined in detail and it was found that the reactivity was accelerated by rise in room temperature in proportion with the magnitude of the reactivity itself. This fact can be explained by the fact that the reactivity of vessels is controlled by the tonus of the vasomotor, especially of the vasodilator, which changes with the environmental temperature.
6. Effects of humidity on the temperature reaction was proved to exist, but not so marked as those of room temperature.
7. Making use of the above experimental results, a method was devised to eliminate the errors in the temperature reaction due to the change of room temperature, and to evaluate the resistance index at the standard temperature of 20°C. from measurements at other temperatures. It was found that 81%-94% of values thus corrected coincided with those actually measured at 20°C. withinthe scope of experimental error, when the room temperature was between 15C°C. to 25°C.