The ability of the normal body to maintain the relative constancy of its fluid matrix has attracted the attention of physiologists since the days of Claude Bernard. Recently, Cannon1 has written on the mechanisms, as far as they are known, by which the organism preserves its chemical and physiologic equilibrium. Should the blood sugar fall below a critical level, the sympathicosuprarenal apparatus operates to provoke glycogenolysis. If metabolic products are thrown rapidly into the blood stream, as during exercise, the heart, lungs and kidneys respond, and, by rushing oxygen and nutriment to the involved tissues and excreting the waste products, restore the body quickly and efficiently to its normal state. The discomforting sensations of hunger and thirst act as sentinels to give warning of the need for nourishment and are thus considered essential features of the general phenomenon of homeostasis, or the ability of the body to resist change.