188 Metabolism of Healthy Man. 



Heat Elimination and Heat Production. 



Methods and Apparatus for Determining the Heat Elimination. 



The estimation of the total heat produced by man is possible in two ways. 

 One method measures directly the heat radiated and conducted from the body- 

 surface, making due allowance for the heat of vaporization of water from the 

 lungs and skin, and for the changes in temperature of the body, as well as the 

 sensible heat of excreta. The other method involves a study of the gaseous 

 exchange from which are computed the kinds and amounts of materials katab- 

 olized. From the heats of combustion of these katabolized materials, and the 

 well-known relationship between the energy of urine and the urinary nitrogen, 

 an attempt is made to compute the energy transformations without the direct 

 measurement, namely, by so-called " indirect calorimetry." It is impossible 

 here, however, to enter into a detailed discussion of the relative merits and 

 accuracy of these two methods. In the experiments here presented, we have 

 the direct measurement of the energy transformations, and we do not depend 

 in any way upon the chemical analyses of the expired gases. The results can, 

 therefore, be considered from the standpoint of a physical experiment in which 

 the energy liberated from the body in the form of heat and the energy required 

 to vaporize the water leaving the lungs and skin may be measured directly. 



An examination of the literature shows that calorimeters for use with man, 

 particularly calorimeters tbat have been carefully calibrated and tested so as 

 to prove their worth for accurate observations, are few in number. The calo- 

 rimeters of the French investigators, including the emission calorimeter of 

 Hirn, 1 have been of especial value in experiments where large amounts of heat 

 are involved, as in experiments during muscular work. The use of the water- 

 bath in which the temperature is raised by the heat production of the body 

 has also made valuable contributions to the study of human calorimetry. Not- 

 withstanding these facts, however, with the exception of the Pashutin " respira- 

 tion calorimeter, which has been used so successfully by Likhatscheff, we know 

 of no form of calorimeter suitable for experiments with man which has an 

 accuracy approximating that of the respiration calorimeter developed origin- 

 ally in the chemical laboratory of Wesleyan University, 3 and with which the 

 experiments reported in this memoir were made. Indeed, it appears from a 

 careful examination of all the earlier recorded data that by reason of their 

 incompleteness very few, if any, of the earlier experiments can be properly 

 compared with tbe experiments made with the new apparatus, in which atten- 

 tion was given to the minutest detail with the view of studying with the 

 greatest accuracy not only the heat elimination but likewise the heat production 

 of man during a given experimental period. 



1 Hirn, Recherches sur l'equivalent mecanique de la chaleur, Paris, 1858. 

 - Likhatscheff, loc. cit. 



3 Atwater and Rosa, U. S. Dept. Agr., Office Expt. Stas. Bui. 63, 1899; Atwater and 

 Benedict, Carnegie Institution of Washington Publication No. 42, 1905. 



