THE GENERAL NATURE OF DIET 



141 



of their various nutrients. In its practice elaborate and very extensive 

 apparatus is sometimes required, and the conduct of the experiments 

 involves much careful complex chemical analysis and attention to the 

 finer points of 'several branches of physics. 



FIG. 73 



PAN /FOR REGULATING REr , JLATOR 



J AIR CURRENT) REGULATOR 



ABSORPTION SYSTEM 



General plan of the respiration-calorimeter laboratory of the United States Department of 

 Agriculture, Washington. This diagram is self-explanatory, so far as the principles of the action 

 of the calorimeter are concerned. The details are very complex. (Atwater.) 



