The constancy in the basal metabolism of human beings has been emphasized recently by Lusk and DuBois,1 who compiled data showing that a man between 30 and 40 years of age may show a basal metabolism during eleven years within a variation of ± 7.6 per cent. Zuntz2 likewise recorded his basal metabolism at intervals over a period of twenty-nine years with little variation. Other physiologic measurements such as body temperature, pulse rate and, in lesser degree, blood pressure under favorable conditions show a similar uniformity.
A high environmental temperature is an important factor in altering this uniformity in physiologic reactions, and often in certain industries marked deviations from the normal occur in workmen who are daily exposed to abnormally high temperatures.
While the human body has the ability to adapt itself to a fairly wide range in temperatures, its capacity for adjustment is limited. It has been stated in