NORMAL PEOCESSES OF ENERGY METABOLISM 551 



Making further corrections for the heat of imbibition and of solution this 

 figure in the particular experiment cited was reduced to 4.42 Cal. which 

 was 76.8 per cent of the gross heat value of the protein as fed. 



Since 100 grams of the dried albumin of meat contained 16.59 gm. 

 of N and its combustion gave a heat value of 4.424 Cal. per gram each 

 gram of N" had a heat value of 26.66 Cal. 



With unwashed meat the value came out 25.98 calories per gram. In 

 the same research Rubner(d) calculated that the body protein of a starving 

 rabbit had a physiological heat value of 3.842 Cal. per gram, or 71.9 

 per cent of its gross heat value, or again 24.94 calories per gram of ~N. 



The mean physiological heat value for a number of animal proteins 

 paraglobulin (4.371), egg albumin (4.307), casein (4.404), fibrin (4.179) 

 was found to be 4.21 Cal. per gram. Conglutiii was taken as a type of 

 vegetable protein and was found to have a value of 3.97 calories. 



Since out of 100 grams of mixed protein in human food about 60 

 per cent is taken from animal sources and 40 per cent from vegetable, Rub- 

 ner calculated the mean value for food protein in general at 4.11 Cal. 

 per gram. 



Accepting the bomb values of Stohmann for carbohydrates and con- 

 sidering the preponderance of starch in human dietaries Rubner estimated 

 the physiological heat value of carbohydrates in general (making deduc- 

 tion of cellulose) at 4.1 Cal. per gram. For fat he adopted the mean 

 value of 9.3 Cal. 



These values Proteins 4.1 Cal. 

 Fat 9.3 " 



C. H. 4.1 " have become standard in the liter- 

 ature of metabolism and are now generally used. 



Atwater and his collaborators in this country have adopted a some- 

 what different method of arriving at the physiological heat value of the 

 foodstuffs. He lays down the principle that the combustible value to the 

 body is found by subtracting from the heat of combustion of the utilizable 

 food the heat value of the urine corresponding to the food in question. 

 The average utilization (i. e., ingestion less feces) of the several classes 

 of foods he gives as follows (Atwater, Benedict, Smith and Bryant) : 



Prot. Fat C. H. 



Animal Foods 97% 95% 98% 



Cereals 85 90 98 



Legumes dry 78 90 97 



Sugar and Starch . . 98 



Legumes, fresh 83 90 95 



Fruits 85 90 90 



The fats and carbohydrates being completely burned in the body, the heat 

 value to the body is equal to the total calorimetric value of the portion ab- 



