It has been 300 years since the publication, in 1614, of the classic observations of Sanctorius on what is still commonly designated as "insensible perspiration," the usually invisible losses of the body now known to be carbon dioxide and water. The science of nutrition was inaugurated with the demonstration that there are considerable losses in body weight during periods in which neither urine nor feces are passed from the body. Thus it became possible to attempt an accounting of the balance of matter in the organism, when the insensible as well as the visible losses could be estimated.
The invisible gaseous emanation from the body has a special significance in that, through the vaporization of water, it serves as a mode of eliminating heat. As heat is a manifestation of metabolism, it is obvious that the insensible perspiration plays some part in the calorimetric functions of the organism. From a