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 nutrition 
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 
