Nov. 22, 1915 Improved Respiration Calorimeter 341 



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 lovver 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° 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 tem.perature 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. 



