300 
Journal of Agricultural Research 
Vol. V, No. 8 
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 (1, 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 
