378 SOURCES OF HEAT. 



Instead of the water-calorimeter the ice-calorimeter may be employed. In 

 this instrument the inner container is surrounded with ice instead of with water. 

 Around this in a second container is still more ice, which prevents any heat 

 from without acting upon the ice in the interior. The body in the interior cham- 

 ber gives off heat and causes a portion of the surrounding ice to melt, while the 

 ice-water passes off below through a tube and is measured. In this connection 

 it should be noted that 79 heat-units are required to melt i gram of ice into i 

 gram of water at a temperature of o C. For animal experimentation the calor- 

 imeter has probably reached the highest grade of perfection at the hands of Rubner. 



The air-calorimeter of d'Arsonval permits of measurement in human beings 

 within a few minutes. A rigid cylinder of woolen material, within which a man 

 may stand, is provided above with a chimney. If the man heats the air in the 

 interior, this will escape through the chimney and set in motion a small wind- 

 mill contained therein, whose revolutions can be counted. The amount of 

 heat given off is proportional to the square of the velocity of the escaping cur- 

 rent of air. A man in the nude state yielded 124, and in the dressed state 79 

 calories in an hour. 



Just as in the calorimeter, though much more slowly, nutrient mat- 

 ters are consumed in the human body with a supply of oxygen, and as a 

 consequence there takes place a transformation of potential into kinetic 

 energy, which in a person at rest appears almost wholly as heat. 



Favre and Silbermann, Frankland, Rechenberg, Stohmann, B. Danilewsky, 

 Jlubner and others have made calorimetric observations as to the amount of heat 

 yielded by the combustion of many nutrient substances. One gram of water- 

 free substance yields in heat-units as follows: 



CARBOHYDRATES. 



Proteids on the average, ........ S7 11 Galactose, .................... 37 22 



Serum-albumin, ............... 5918 Cane-sugar, ................... 3955 



Egg-albumin .................. 5735 Milk-sugar, .................... 395 2 



Syntonin, ..................... 598 Maltose, ...................... 3949 



Hemoglobin, ..... .............. 5885 Glycogen, ..................... 4191 



Milk-casein, ................... 5858 Starch, ....................... 4183 



Yolk of egg, . . . : ............... 5841 Cellulose, ..................... 4185 



Vitellin, ....................... 5745 Cow's milk, ................... 5613 



M _ af f 5663 Woman's milk .................. 5786 



\ 5641 Rye-bread ..................... 4471 



Peptone, ...................... 5 2 99 Wheat-bread, ................. 43 5 1 



Fibrin, ........................ 5637 Peas .......................... 4889 



Vegetable fibrin, ............... 594 2 Buckwheat, ................... 4288 



Legumin, ..................... 5793 Maize, ........................ 5188 



Conglutin, .................... 5479 Alcohol, ...................... 6980 



Muscle-extractives, ............. 4400 



Animal fats on the average, ..... 9500 Liebig's meat-extract ........... 3216 



Butter 9 2 3i (Principally according to Stoh- 



Olive-oil, '.'.'.'.'.'.'.'.'.'. '.'.'.'.'.'.'.'.'.'.'/ 9*7 mann >- ' 



( 900 



T> ., 



Ra P e - 011 ' 



9627 Urea ......................... 2 537 



9759 Glycin, ................... .... 



Stearic acid, ................... 2712 Leucin, ....................... 6533 



Oleic acid, .................... 2682 Hippuric acid, ................. 5678 



Palmitic acid, ................. 2398 Kreatinin, ..................... 4275 



Glycerin, ..................... 397 Uric acid, ........... . ......... 2 74* 



Alcohol, ...................... 7 100 



As the proteids in the body are not transformed beyond urea the amount 

 of heat resulting from the combustion of urea is to be deducted from that resulting 

 from the combustion of the proteids. As one gram of proteids (average calories 

 5711) yields 0.3428 gram of urea, and i gram of urea yields 2537 calories, 870 

 calories are to be deducted. 



Isodynamic food-stuffs, namely, those that yield the same amount of heat 

 in the process of combustion, are as follows: 100 grams of animal proteid, after 

 deduction of the heat resulting from the combustion of urea, equal 52 grams of 

 fat, 114 grams of starch, 128 grams of dextrose. One hundred grams of fat are 



