I. INTRODUCTION In 1620, Sir Francis Bacon wrote: "Let further inquiry be made into the different degrees of heat in different parts and limbs of the same animal. For milk, blood, seed, eggs, are found to be hot only in a moderate degree, and less hot than the outer flesh of the animal when in motion or agitated. But what degree of heat is in the brain, stomach, heart, etc., has not yet been in like manner inquired." 1 Since this was written surprisingly few studies have been made of the actual temperatures of different parts of the body, although there has been great interest in other aspects of metabolism. As early as 1614, Sanctorius in Venice made the first attempt to solve the subtle problems of metabolism, but it was not until 1780, when Lavoisier began his far-reaching investigations of the chemistry of life that the modern science of