Physiological Insulation of Swine as Bare-Skinned Mammals

Abstract

Temperatures on the bare skin and underlying tissue gradients were measured in swine during winter and summer in Alaska. The swine were of the cross Landrace and Hampshire, called Hamprace. At rest, the skin temperature, which was as low as 9°C in cold air, varied topographically. Over the shoulders and on the upper part of the body, skin temperature was uniform during constant conditions, but ears and legs might be quite different. Change from rest to moderate activity promptly elevated the temperature on the surface of the shoulders. In gradient measurements maximum temperatures, found at depths 45 to 70 mm, were 38.4 ± 0.5, practically constant. Gradient curves extended, mostly with small parabolic but no discontinuous curvature, outward to the cooler skin temperatures. The temperature of skin on the shoulder cooled to 9°C in air at –12°C. The cooling curve of the bare skin became asymptotic when the skin cooled to 15°C in air at 0°C, indicating the limit of vasoconstriction and the residue thereafter of maximal insulation by the superficial tissues. Because of ability to cool, the bare-skinned superficial layers of swine afford insulation superior to that of naked man. Since the cold tissues regularly act for heat conservation they remain operative and integrated with the body at temperatures surprisingly low for tissues of warm-blooded animals. This heterothermism in bare-skinned mammalian tissues is effectively utilized for the heat regulation of the homeothermous body. Submitted on April 9, 1956