PHYSIOLOGICAL REACTIONS OF THE HUMAN BODY TO VARYING ENVIRONMENTAL TEMPERATURES

General object of present experiments. The fact that the human body ad-justs itself to low environmental temperatures chiefly by constriction of the peripheral blood vessels, and to high atmospheric temperatures chiefly by increased secretion of sweat has long been a truism of physiology. We know 1, that physical regulation through constriction or dilatation of vessels is essentially a change in conductivity over the gradient between environ-mental and internal body temperature (Kleiber, 1932, Burton, 1934) ; and 2, that various segments of the body play relatively different roles in the elimination of heat (Maddock and Coller, 1933; Freeman, 1934). It has generally been assumed that insensible evaporative loss for subjects at rest is a roughly constant proportion of the total heat loss within the zone of thermal neutrality (Soderstrom and DuBois, 1917; Benedict and Root, 1926), provided the hydration of the body is normal (Manchester, 1931), the subjects not pathological (Lazlo and Schurmeyer, 1931), the humidity constant (Wiley and Newburgh, 1931), and the subjects in a post-absorp-