Nov. 22, 1915 Improved Respiration Calorimeter 301 



the one used for over 12 years in the laboratory of Prof. Atwater. In 

 1907, when because of illness he discontinued his connection with the 

 research, the respiration calorimeter was transferred to Washington. 

 To move the apparatus it was necessary to dismantle it completely, so 

 that to set it up again in the laboratory provided for it in the new building 

 of the Department involved its practical reconstruction. Advantage was 

 taken of the opportunity thus afforded to modify it in many important 

 details, with special consideration for simplicity of structure and conve- 

 nience of operation. The reconstructed apparatus has been briefly 

 described in a former publication of the Department (15) and elsewhere 

 (14). The experience with this apparatus has suggested further improve- 

 ments that have been incorporated from time to time, with the result that 

 the work of conducting an experiment with the respiration calorimeter is 

 much less than formerly, and a degree of accuracy of measurement is 

 obtained that was not possible with the apparatus in its earlier state. 

 The present publication describes this greatly improved respiration 

 calorimeter in detail. A general view of the apparatus is shown in Plate 

 XXX. 



PRINCIPLE OF THE RESPIRATION CALORIMETER 



The principle of the respiration calorimeter now in use in the nuti-ition 

 investigations is the same as that of the later form of the apparatus 

 employed in the investigations formerly conducted at Wesleyan Univer- 

 sity. For the determination of gaseous exchange the device is similar to 

 the respiration apparatus of Regnault and Reiset (17), having a respira- 

 tion chamber and a system of air-purifying devices connected in series in 

 a closed circuit. The air confined in the circuit is kept in circulation, the 

 respiratory products imparted to it by the subject in the chamber being 

 constantly removed and oxygen constantly supplied to replace that used 

 by the subject. For the determination of heat produced in the chamber 

 the device is a constant-temperature, continuous-flow, water calorim- 

 eter, in which the calorimetric features of the original Atwater-Rosa 

 apparatus are retained. These provide for preventing the passage of 

 heat through the walls of the chamber and for taking up the heat by a 

 current of cold water as fast as it is generated in the chamber. The 

 determination of respiratory exchange and energy transformation, to be 

 of value, demands a high degree of accuracy in the fundamental measure- 

 ments, and it follows that the instrument with which they are made 

 must be precise and finely adjusted, sensitive to slight changes within, 

 and protected from the effects of fluctuations occurring outside of it. 



Of fundamental importance in the device is a chamber with walls that 

 are air-tight and heatproof. It must be so large that the subject may 

 live in it in comfort during the time of an experiment, which may con- 

 tinue several hours or several days, and yet not so large that its volume 



