That the body constantly loses weight through the skin and respiratory passages in the form of water vapor and gases1 has long been known. The exact nature of this phenomenon is still a moot question. Investigators differ as to whether it is a matter of physical diffusion2 or an active physiologic process3 and as to whether it is partly4 or entirely5 dependent on the activity of the sweat glands or occurs independently.6 All observers, however, agree that this loss of weight, although invisible, intangible and insensible, is weighable.
That the investigation of the so-called perspiratio insensibilis constituted one of the attractive medical problems of ancient days is evidenced by the aphorisms of Hippocrates and Galen.7
What was probably the first quantitative measurement of the insensible perspiration was made by Sanctorius,8 in 1614, by means of a crude balance of his own construction.
GINANDES GJ, TOPPER A. INSENSIBLE PERSPIRATION IN CHILDREN: EXPERIMENTAL PROCEDURE AND THE INFLUENCE OF CERTAIN FACTORS. Am J Dis Child. 1936;52(3):528–551. doi:10.1001/archpedi.1936.04140030018002
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