300 Journal of Agricultural Research voi. v. No. s 



with alteration in detail in accordance with modification in methods of 

 investigation, but in its equipment for the measurement of the output 

 of heat it was quite original. Prof. E. B. Rosa, then of Wesleyan Uni- 

 versity and associated with Prof. Atwater in the investigations, devised 

 a method of preventing the passage of heat through the walls of the 

 respiration chamber, and provided for carrying out and measuring the 

 heat generated within it. The term "respiration calorimeter" was 

 applied to the Atwater-Rosa device to indicate that it performed simul- 

 taneously the functions of both a respiration apparatus and a calorimeter. 

 Experiments with the respiration calorimeter have been continued as 

 part of the nutrition investigations of the Department of Agriculture 

 during the 20 years or more since they were begun. With the progress 

 of the work many modifications have been introduced for the purpose of 

 making the apparatus simpler, easier, and more economical to operate 

 than the original, while yielding more complete and more accurate data. 

 Descriptions of the apparatus in its original form and its later modifica- 

 tions, and the results of a large number of experiments with it, have 

 appeared in former publications of the Department (i, 2, 3, 4, 6, 9) and 

 have become a part of the data commonly included in textbooks and 

 works of reference. 



As a result of the work of Atwater and his associates, the investigator 

 has been provided with an apparatus of precision and a method of investi- 

 gation which, with adaptation in different laboratories to meet varied 

 experimental conditions, have proved valuable for a range of work even 

 wider than was originally anticipated. In the nutrition laboratories 

 of the Department of Agriculture it has been employed in the form 

 described in the present publication in studies of the utilization of food 

 and the performance of muscular work, and a recent development, to be 

 described in detail in a later publication, has been adapted to studies of 

 problems in plant physiology. At the Institute of Animal Nutrition, 

 State College, Pa., Dr. H. P. Armsby employs a respiration calorimeter, 

 which he has adapted from the original Atwater-Rosa type of apparatus, 

 in investigations of the nutrition of farm animals conducted in coopera- 

 tion with the Department of Agriculture. In other inquiries besides those 

 of the Department respiration calorimeters have proved of great value in 

 investigations of different but related character. Investigators have 

 modified and improved the original form to suit their special needs, 

 though this method of research has long passed the experimental initial 

 stage and has become recognized as possessing great possibilities where 

 accurate measurements of energy values and gaseous exchange are needed 

 to supplement the data which the investigator secures by other methods. 



The respiration calorimeter employed at the present time in the nutri- 

 tion investigations of the Department of Agriculture is a development of 



