THERMAL EXCHANGES BETWEEN THE BODY AND ITS ENVIRONMENT

Everyday clinical experience bears witness to the conclusion that departures from the so-called normal body temperature are among the fundamental physical signs of disease. The invariable use of the clinical thermometer attests its importance. It has become imperative, therefore, to understand the laws that govern the maintenance of temperature equilibrium in a body that is living ordinarily under widely fluctuating environmental temperatures while it may be experiencing considerable variations in internal heat production. As a recent writer has summarized the problem, energy is dissipated from the body as mechanical energy through work performed and, to a greater extent, as heat energy through radiation, convection and evaporation of moisture. Heat loss by radiation, convection or evaporation of moisture must necessarily be in accordance with well known physical laws. Radiation and convection depend on the temperature difference between the body and its environment, and also on the insulation or clothing worn. Evaporation