48 CALORIMETERS FOR STUDYING RESPIRATORY EXCHANGE, ETC. 



(see page 71) partly distended is shown connected to the ingoing air-pipe, 

 and on the top of the calorimeter connected to the tension equalizer is a 

 Sonden manometer. On the floor at the right is seen the resistance coil 

 used for electrical tests (see page 50). A number of connections inside 

 the chamber at the left are made with electric wires or with rubber tubing. 

 Of the five connections appearing through the opening, reading from left 

 to right, we have, first, the rubber connection witli the pneumograph, then 

 the tubing for connection with the stethoscope, then the electric-resistance 

 thermometer, the telephone, and finally a push button for bell call. The 

 connections for the pneumograph and stethoscope are made with the in- 

 struments outside on the table at the left of the bed calorimeter. 



MEASUREMENTS OF BODY-TEMPERATURE. 



While it is possible to control arbitrarily the temperature of the calo- 

 rimeter by increasing or decreasing the amount of heat brought away, and 

 thus compensate exactly for the heat eliminated by the subject, the hydro- 

 thermal equivalent of the system itself being about 20 calories on the 

 other hand the body of the subject may undergo marked changes in tem- 

 perature and thus influence the measurement of the heat production to a 

 noticeable degree ; for if heat is lost from the body by a fall of body-tem- 

 perature or stored as indicated by a rise in temperature, obviously the heat 

 produced during the given period will not equal that eliminated and meas- 

 ured by the water-current and by the latent heat of water vaporized. In 

 order to make accurate measurements, therefore, of the heat-production as 

 distinguished from the heat elimination, we should know with great accuracy 

 the hydrothermal equivalent of the body and changes in body temperature. 

 The most satisfactory method at present known of determining the hydro- 

 thermal equivalent of the body is to assume the specific heat of the body 

 as 0.83.* This factor will of course vary considerably with the weight of 

 body material and the proportion of fat, water, and muscular tissue present 

 therein, but for general purposes nothing better can at present be employed. 

 From the weight of the subject and this factor the hydrothermal equivalent 

 of the body can be calculated. It remains to determine, then, with great 

 exactness the body temperature. 



Recognizing early the importance of securing accurate body-temperatures 

 in researches of this kind, a number of investigations were made and pub- 

 lished elsewhere f regarding the body-temperature in connection with the 



*Pembrey: Schafer's Text-book of Physiology, vol. 1, p. 838. (1898.) 

 | Benedict and Snell: Korpertemperatur Schwankungen mit besonderer Riick- 

 sicht auf den Einfluss, welchen die Umkehrung der taglichen Lebensgewohnheit 

 beim Menschen ausiibt. Archiv f. d. ges. Physiologie, Bd. 90. p. 33. (1902.) 



Benedict: Studies in body-temperature: I. The influence of the inversion of 

 the daily routine: the temperature of night-workers. American Journal of Phy- 

 siology, vol. 11, p. 145. (1904.) 



