112 Metabolism of Healthy Man. 



proportions of carbohydrates and fat. It is highly improbable that the loss of 

 several hundred grams of water per day, shown in the period with fat diet, 

 would continue a month or more, and, as stated previously, changes in body- 

 weight are to be taken, therefore, as of significance only when the experiment 

 continues for a period of several weeks. Certainly, for short experiments, body- 

 weight is for the most part wholly without significance. 



INSENSIBLE PERSPIRATION. 



Studies of other investigators. Aside from the fluctuations in body-weight 

 which may be, as we have seen, fluctuations in large part of preformed water 

 in the tissues of the body, there is an interesting observation in regard to 

 changes in body-weight which the experiments here presented throw much 

 light upon, namely, the so-called " insensible perspiration." The early observa- 

 tions of Sanctorius showed that the body is continually undergoing a loss, and 

 recuperating after every meal, the loss being gradual save when urine or feces 

 are passed. Singularly enough, these investigations of Sanctorius were not 

 supplemented by any of scientific value until the exceedingly exact investiga- 

 tions of Lombard. While Sanctorius utilized his knowledge of the insensible 

 perspiration, that is, the loss by gaseous emanations from the body, he made 

 no careful study other than could be made with a crude form of steelyard. In 

 recent years Lombard has attacked the problem with much success and has 

 succeeded in constructing a most sensitive balance upon which the subject can 

 be weighed, and variations in weight amounting to but a few milligrams are 

 graphically recorded. His observations have thus far been confined to noting 

 the loss in weight during short periods with normal respiration and when the 

 subject holds his breath. Under the latter conditions the data regarding the 

 cutaneous respiration are obtained. The possibilities of studying the gaseous 

 emanations by this method are well set forth in his discussion of the apparatus. 1 



Insensible Loss by Gaseous Exchange an Aid in Obtaining Intermediate 



Body-Weights. 



In connection with the metabolism experiments made at Wesleyan University, 

 the importance of securing accurate measures of body-weight led ultimately to 

 a study of the insensible perspiration and, as determined from the gaseous ex- 

 change, the insensible losses are now taken into consideration in obtaining 

 intermediate body-weights when desired. All the ingesta and egesta in these 

 experiments are carefully measured, hence it is not difficult to correct an 

 initial body-weight for the sudden fluctuations due to drinking of water, taking 

 of food, passing urine, or defecation, and thus determine the body-weight at 

 different hours of the day. Making these allowances, it is possible, therefore, 

 to construct a curve showing the gradual loss in weight, i. e., the insensible 

 perspiration. Few people realize that there is a persistent gradual loss in 



1 Lombard, Journ. Amer. Med. Assoc, 1906, 47, pp. 1790-1793. 



