NUTRITION INVESTIGATIONS. 447 



ments of heat and mechanical work, Professor Atwater was assisted by 

 Dr. E. B. Rosa, professor of physics in Wesleyan University, and 

 others. Several years were spent in the development of this apparatus 

 and the elaboration of methods of experimenting with it. 



The Atwater-Rosa respiration calorimeter is an air-tight copper box 

 inclosed in zinc and wooden cases and of such a size that a man can 

 remain in it in comparative comfort for a number of days. In experi- 

 ments conducted at Middletown, Conn., a man has remained in the 

 apparatus some two weeks. The copper box or chamber is some 7 feet 

 long, 4 feet wide, and 6 feet high. It is provided with a folding cot, 

 table, and chair. Food and other necessary articles are passed in 

 and out through a tube at one side of the chamber. A window in 

 front admits light, and the man inside of the chamber can communi- 

 cate with those outside by means of a telephone. The chamber is 

 supplied with fresh air, and the amount and composition of the air 

 which enters and leaves it are determined, the latter containing the 

 products of respiration. The amount and composition of the food and 

 excretory products are also determined. The heat given off b} r the 

 man's body is measured, as well as the heat value of the food and 

 excreta. A stream of cold water of known temperature and volume 

 circulates through the interior of the chamber in pipes. It absorbs 

 the heat given off by the man's body, and permits of its measurement, 

 at the same time serving to keep the temperature of the interior cool. 



At the present time the respiration calorimeter is being much 

 improved, and it is expected that in the near future it may be made 

 into a so-called closed circuit apparatus, in which the air drawn from 

 the respiration chamber is freed from its carbon dioxid, oxygen added, 

 and the air returned to the chamber. When this is accomplished, the 

 apparatus will permit of still more valuable and accurate research. 



METABOLISM EXPERIMENTS. 



The development of apparatus and methods has been both costty and 

 time-consuming, but the results bid fair to be of no little value in 

 determining the physiological demands of the human body under dif- 

 ferent conditions, in studying the way different foods are used in the 

 body, and in carrying out various abstract lines of physiological 

 research. In some of the experiments the subject worked very hard 

 driving a stationary bicycle; in others, he worked as little as possible, 

 spending his time in reading or writing. In the work experiments 

 the amount of work performed was measured. Such experiments 

 show the value of different foods for the production of work and serve 

 as a means for judging the power of the human body considered as a 

 machine. The results of nineteen experiments covering sixty-five days 

 have already been published in bulletins of the Office of Experiment 



