42 6 THE POPULAR SCIENCE MONTHLY 



and his associates in Bonn, by Zuntz in Berlin, by Tschudnovski, 

 Pashutin, and others in St. Petersburg, by Tigerstedt in Sweden, and by 

 many others. 



The energy exchanges of the organism have a fundamental bearing 

 in dietetics, since the heat output of the body under different conditions 

 determines the caloric requirements of the diet. The apparatus used to 

 investigate these exchanges, the respiration calorimeter, besides meas- 

 uring the respiratory products after the manner of Pettenkofer's appa- 

 ratus, determines with great accuracy the amount of heat given off by 

 the subject. In its perfected form this mechanism is a marvel of com- 

 plexity, elaborateness, and delicacy, requiring much labor and ample 

 resources for its construction and operation. 



Some imperfect calorimetric studies on animals and man were pub- 

 lished by Russian observers from 1884. Max Eubner (18.5-4- ) was 

 the first to conduct a successful and elaborate series of calorimetric 

 observations on animals. He was educated at Munich under Toit; 

 professor at Marburg 1885-1891; at Berlin from 1891, succeeding Koch 

 as Director of the Hygienic Institute. His studies were begun about 

 1889, and his results published in full in 1902. He demonstrated that 

 the law of the conservation of energy holds good for animals; and he 

 has laid down principles fundamental in this branch of physiology and 

 of the utmost importance in dietetics. 



The most elaborate calorimetric investigations ever carried out have 

 been those prosecuted in this country since 1892 by Wilbur Olin Atwater 

 (1844—1907) and his associates and successors. Atwater studied at 

 Munich under Voit, and derived some of his ideas from Eubner. Pro- 

 fessor of chemistry at W^esleyan University, Middletown, Connecticut, 

 from 1873 until his death, he devoted his whole life to investigations 

 concerning food and nutrition. In 1892, with the assistance of the 

 physicist Rosa, he began the construction at Wesleyan University of a 

 respiration calorimeter large enough to accommodate a human subject. 

 This apparatus underwent gradual improvement imtil finally direct 

 determinations of the oxygen exchanges were, for the first time on a 

 large scale, carried out. The work was jointly supported by "VTesleyan 

 Universit}', the Storrs (Connecticut) Agricultural Experiment Station, 

 the United States Department of Agriculture, and (later) the Carnegie 

 Institution. "With this apparatus an elaborate series of researches was 

 carried out from 1892 to 1907, the results of which must stand as 

 classical. After Atwater's death in 1907, the original apparatus was 

 removed to "Washington and installed in the Department of Agriculture, 

 where it is now in operation ; while his successor Francis Gano Benedict 

 under a grant from the Carnegie Institution is continuing the research 

 with an equipment constructed in Boston. 



Other investigators have since taken up this line of work, and impor- 



