528 ENERGY EXCHANGE AFTER FOOD 



protein, the amount of energy which is lost in the urine 

 and faeces must be deducted from the total energy which is 

 obtained by burning the protein in a calorimetric bomb; 

 and in case exactness is important there must also be sub- 

 tracted the swelling- and solution-heat of the protein and the 

 solution- heat of the dried urinary substance. 



In an experiment of Buhner's 29 one gram of muscle pro- 

 tein was found to yield directly a combustion heat of 5754.0 

 small calories; of which 185.4 calories were lost with the 

 fasces and 1094.5 calories with the urine. In addition 28.8 

 calories were taken up as solution- and swelling-heat of the 

 protein and 21.5 calories as solution-heat of the urinary sub- 

 stances. There remained, therefore, 4423.8 small calories 

 as the specific physiological utilization value of one gram of 

 protein. Eubner estimated a somewhat smaller value for 

 the protein of the ordinary mixed diet of man, and as already 

 stated, proposed the following standard figures : 



1 g. Protein 4.1 large calories 



1 g. Fat 9.3 large calories 



1 g. Carbohydrate 4.1 large calories 



Slightly different standard values have been proposed by 



Atwater and by the Zuntz school (protein, 4.31; fat, 9.46 



starch, 4.18). 30 



The exactness of these values is shown by the following : 

 Eubner determined in a dog the heat production and gas 

 interchange. From analysis of the latter and of the urine 

 and faeces it was calculated just how much protein, fat and 

 carbohydrate were actually consumed, and how much heat, 

 therefore, the animal must have produced. Comparison of 

 this theoretically computed heat production with direct ob- 

 servation of heat production showed an almost complete 

 agreement (a difference of between one-half and one per 

 cent.). 



29 Cited by F. Tangl, Ergebn. d. Physiol., 3", 45, 1909. 



80 Cf. Literature: A. Lowy, Handb. d. Biochem., 4', 280, 1908. 



