FATS, CARBOHYDRATES, AND ALBUMINS. 333 



being that amount of heat required to raise 1 gram of water from to 

 1 C. A large calorie (Cal.) is the amount of heat necessary to raise 1 kilo- 

 gram of water from to 1 C. We shall use the large calorie in every 

 case to express the heat values of individual food materials. 



Complete oxidation of one gram of each of the following articles of food 

 in a calorimetric bomb gave the following values: 



Calories 



Casein 5.86 



Egg- albumin 5.74 



Conglutin 5.48 



Average value for protein 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 



The values given for the carbohydrates and fats represent exactly the 

 amount of heat which is liberated during combustion in the animal organ- 

 ism. The animal cells likewise oxidize the carbohydrates and fats to 

 carbon dioxide and water. The physiological heat value of the fats is 

 generally given as 9.3 calories, and of the carbohydrates 4.1 calories 

 for each gram of substance. The values in the table do not apply to the 

 albumins as oxidized in the living organism. The animal cell does not 

 utilize completely the energy present in albumin. A portion of this energy 

 goes to waste, usually in the form of urea. We are indebted to Rubner l 

 for an exact estimation of the physiological heat value of albumin. He 

 fed a dog exclusively on washed meat, whose heat value had been care- 

 fully determined. From this he subtracted the heat values of the urine 

 and faeces, as well as that necessary for the swelling of the albuminous 

 material and for dissolving the urea. In like manner Rubner determined 

 the heat of combustion of the decomposed albumin in the body of a fasting 

 rabbit. He found the following values for the physiological heat of com- 

 bustion for each gram albumin: 



One gram of dry substance Calories 



Albumin from meat 4.4 



Lean meat .4.0 



Albumin during fasting 3.8 



The physiological heat of combustion is not identical for the different 

 proteins. The normal value for animal albumin is estimated as 4.23 



1 Max Rubner: Z. Biol. 21, 250 and 337 (1885). Berthelot and Vielle: Compt. rend. 

 102, 1284 (1886). Berthelot and Recoura: ibid. 104, 875, 1571 (1887); Berthelot and 

 Andre": 110, 884 and 925 (1890). F. Stohmann: Z. Biol. 31, 364 (1895). 



