CALORIC VALUES OF FOOD-STUFFS. 885 



calculate the part taken by the fats and carbohydrate will be shown in connection 

 with the calculation of the energy metabolism. 



The quantity of water and mineral bodies voided with the urine and 

 feces can easily be determined. The quantity of water eliminated by 

 the skin and lungs may be directly estimated by means of the large 

 respiration apparatus. 



The organic constituents of the body as well as the foodstuffs intro- 

 duced, represent a sum of chemical' energy which the body can use 

 for force. The exchange of material is also an exchange of force, 

 and the first stands in such close relation to the second that the study 

 of one cannot be separated from the other. The energy theory of 

 metabolism has exercised an extraordinarily fruitful influence upon 

 the entire study of metabolism and nutrition, and this is due in great 

 measure to the work of RUBNER. 



This energy of the various foods may be represented by the amount 

 of heat which is set free in their combustion. This quantity of heat is 

 expressed as calories, and a small calorie is the quantity of heat necessary 

 to warm 1 gram of water from to 1 C. A large calorie is the quantity 

 of heat necessary to warm 1 kilo of water 1 C. Here and in the follow- 

 ing pages large calories are to be understood. There are numerous 

 investigations by different experimenters, such as FRANKLAND, DAN- 

 ILEWSKI, RUBNER, BERTHELOT, STOHMANN, BENEDICT and OSBORNE, 

 and others, on the calorific value of different foodstuffs. The following 

 results, which represent the calorific value of a few nutritive bodies on 

 complete combustion outside of the body to the highest oxidation prod- 

 ucts, are taken from STOHMANN'S l work. 



Calories. 



Casein 5 . 86 



Ovalbumin 5 . 74 



Conglutin 5 . 48 



Protein (average) 5.71 



Animal tissue-fat 9 . 50 



Butter-fat 9 . 23 



Cane-sugar 3 . 96 



Milk-sugar 3 . 95 



Glucose 3. 74 



Starch 4. 19 



Fats and carbohydrates are completely burnt in the body, and one can 

 therefore consider their combustion equivalent as a measure of the living 

 force developed by them within the organism. We generally designate 

 9.3 and 4.1 calories for each gram of substance as the average for the 

 physiological calorific value of fats and carbohydrates respectively. 



x See Rubner, Zeitschr. f. Biologic, 21, which also cites the works of Frankland 

 and Danilewski; see also Berthelot, Compt. Rend., 102, 104, and 110; Stohmann, 

 Zcitschr. f. Biologie, 31; Benedict and Osborne (vegetable proteins), Journ. of biol. 

 Chem., 3. 



