STUDIES IN TEMPERATURE SENSATION. I. A COMPARISON OF THE SENSATION PRODUCED BY INFRA-RED AND VISIBLE RADIATION

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Abstract
I. A new technique for the measurement of the thermal sensitivity of the skin to radiation was described; it provided for an objective detn. of the smallest rate of irradiation which will produce sensation. The response of white and negro skin to sunlight, visible light, and infra red radiation was studied. The specific stimulating qualities of the various radiations depended upon the reflecting power of the skin for the different rays and upon the degree of penetration of the radiation into the skin. The effect of natural pigment upon the response to thermal radiation was significant only in the visible portion of the spectrum. The negro subjects were found to be slightly (15%) more sensitive than white subjects to the thermal action of sunlight. II. The thermal changes produced at the skin surface by known amts. of penetrating and non-penetrating radiation were studied with a radiometer. With equal rates of radiation the skin temp. was elevated most by the non-penetrating radiations and progressively less the greater the penetration. Where the strength of the irradiations was adjusted to produce a barely perceptible sensation the skin temp. was elevated highest by the penetrating radiation and least by the non-penetrating radiation. Neither the change nor rate of change of skin temp. could be the stimulus for sensation of warmth and the evidence supported the hypothesis that the sensation was due to a change in the normal thermal gradients in the skin.

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