NOV. 22, 1915 
Improved Respiration Calorimeter 
34i 
occurred in computing the quantity of heat actually produced by the 
body in the period. Conversely, a decrease in body temperature would 
mean that a certain amount of the heat that had accumulated in the body 
previous to the experimental period had been eliminated with that pro¬ 
duced by the body during the period and should be subtracted from the 
quantity measured by the calorimeter in determining the quantity 
actually produced in the period. 
The weight of the body can be ascertained accurately. The specific 
heat assumed is an estimate, but is probably fairly accurate. The tem¬ 
perature of the body as a whole can not be determined precisely, because 
it is not the same in all parts of the body. The temperature at the'sur¬ 
face is noticeably lower than that of the interior, and that of the tissue 
in one region differs from that of the tissue in another. It seems probable, 
however, that, except perhaps at the surface, a change in temperature in 
one part of the body is accompanied by a corresponding change in the 
others; hence, the amount of temperature change, which is the factor 
concerned in the correction here considered, may be ascertained with a 
fair degree of accuracy from measurement of temperature where possible, 
but preferably below the surface. 
By means of an electric-resistance thermometer the temperature of 
the subject in the chamber, at the spot at which the thermometer is 
located, may be ascertained at any given moment by the observer outside. 
A coil of wire of variable resistance, mounted so that it may be worn by 
the subject and kept at the temperature of the body, is connected with 
a Wheatstone bridge on the observer's table, by which the variations in 
resistance of the coil, due to changes in body temperature, may be 
observed, connection between the bridge and the thermometer coil being 
made through the special switch mentioned on page 334. 
One type of thermometer bulb, designed for use in the rectum, is a coil 
of platinum wire having a resistance of 20 ohms at 37 0 C., inclosed in a 
thin steel shell or capsule 5 cm. in length and 5 mm. in external diameter. 
Since this thermometer may be kept in place for considerable periods 
without discomfort, a virtually continuous record of body temperature 
may be obtained, depending upon the frequency of the readings by the 
observer, and fluctuations may be followed for long or short periods as 
desired, but the temperatures at the beginning and end of the experi¬ 
mental period are the ones essential for the correction here considered. 
In another type, designed for measuring temperature of the body surface, 
the wire is wound in a flat spiral coil 15 mm. in diameter, mounted in a 
frame of thin, hard rubber by which it may be held against the skin. 
This coil rapidly acquires the temperature of the skin. 
In some cases the temperature is measured by means of accurate 
clinical thermometers, inserted by the subject under the tongue or in the 
axilla, which are afterward read by the observer. 
