A text-book of physiology for medical students and physicians . at ()to reduce it to so much water, and this product is multiplied by the59 930 NUTRITION AND HEAT REGULATION. difference in body temperature at the beginning and the end of theexperiment. The product is obtained in calories and is subtractedfrom the amount of heat lost, as determined by the calorimeter, toobtain the amount of heat produced. If, on the contrary, the ani-mals temperature has risen during the experiment the body hasproduced more heat than it has dissipated. The increase may bedetermined as above by multiplying th
A text-book of physiology for medical students and physicians . at ()to reduce it to so much water, and this product is multiplied by the59 930 NUTRITION AND HEAT REGULATION. difference in body temperature at the beginning and the end of theexperiment. The product is obtained in calories and is subtractedfrom the amount of heat lost, as determined by the calorimeter, toobtain the amount of heat produced. If, on the contrary, the ani-mals temperature has risen during the experiment the body hasproduced more heat than it has dissipated. The increase may bedetermined as above by multiplying the weight of the animal, thespecific heat of the body, and the difference in temperature. Thisamount added to the heat lost gives the heat produced. Many investigators have used some form of air air calorimeter consists essentially of a double-walled chamberor box with air between the walls. The animal is placed in theinner box and the heat given off is measured by the expansion ofthe air between the walls. Many different forms are used, prefer-. Fig. 301.—DArsonvals differential calorimeter. ence being given to some modification of the differential air calo-rimeter. In this last-named instrument two exactly similar chambersare constructed ; one contains the animal while the other serves as adummy. These two chambers are balanced against each other,the air space in the dummy being heated by immersion in a bath orby burning hydrogen in the interior. As these sources of heat areknown and can be controlled, it is evident that if the dummy ismade to balance exactly the chamber containing the animal theamount of heat given off in each is the same. The principle of thedifferential calorimeter is represented in Fig. 301, which gives aschema of the form originally employed by dArsonval; 8 and 8represent the two calorimeters, in one of which the animal is placedwhile the other acts as dummy. Each is double walled and theair spaces are connected by tubes, 10 and 10, to sm
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