. A text-book of physiology : for medical students and physicians . ° C, or more accurately the amountof heat required to raise 1 gm. of water from 15° to 16° C. Thisunit is sometimes designated as a small calorie to distinguish itfrom the large calorie (C),—that is, the quantity of heat necessaryto raise 1 kgm. of water 1° C. The large calorie is equal to 1000 * For further details see Richet, La chaleur animale, 1889; and Pem-brey, Animal Heat, Schaefers Text-book of Physiology, vol. i, 1898. 948 NUTRITION AND HEAT REGULATION. small calories. In physiology calorimeters have been used for two
. A text-book of physiology : for medical students and physicians . ° C, or more accurately the amountof heat required to raise 1 gm. of water from 15° to 16° C. Thisunit is sometimes designated as a small calorie to distinguish itfrom the large calorie (C),—that is, the quantity of heat necessaryto raise 1 kgm. of water 1° C. The large calorie is equal to 1000 * For further details see Richet, La chaleur animale, 1889; and Pem-brey, Animal Heat, Schaefers Text-book of Physiology, vol. i, 1898. 948 NUTRITION AND HEAT REGULATION. small calories. In physiology calorimeters have been used for twomain purposes: to determine the heat equivalent of foods,—that is,the amount of heat given off when the various foodstuffs are burned,—and, secondly, to determine the heat produced and the heat dissi-pated by living animals during a given period. For the first pur-pose the apparatus that is most frequently employed at present isthe bomb calorimeter devised by Bertheldt. The bomb consistsof a strong steel cylinder in which the food to be burned is placed. Fig. 300.—Reicherts water calorimeter. and which is filled with oxygen. The combustion of the foodstuffis initiated by means of a spiral of platinum wire heated by anelectrical current. The bomb is immersed in water and the heatgiven off raises the temperature of the water a certain numberof degrees centigrade. The weight of water being known, theamount of heat is easily expressed in calories. For the purposeof measuring the heat given off by living animals two principalforms of calorimeter are used, each form having a number ofmodifications. These two forms are the water calorimeter and theair calorimeter. The water calorimeter was the form used in thefirst experiments on record (Crawford, 1779). In principle itconsists of a double-walled box with a known weight of waterbetween the walls. The animal is placed in the inner box and the CALORIMETRY. 949 heat given off is absorbed by the water. Knowing the weight ofthe
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