888 METABOLISM. 



the same number, 5047 calories, are produced. In an analogous manner 

 the average calorific value of fat for 1 liter of oxygen, 4686 calories, and 

 for 1 liter carbon dioxide, 6629 calories, can be calculated. 



These figures, which represent the physiological combustion values 

 per 1 gram of food-stuffs, derived from the carbon dioxide output or the 

 oxygen in-take in (grams or) liters which are represented by the quotients 



' or , ' have been called the calorific coefficients. 



With proteins, because of the unequal composition of the different 

 proteins, the results are uncertain and variable, and the calculation is 

 much more complicated. As example we will give the following calcula- 

 tion of ZUNTZ l for the fat-free dry substance of meat. 



This substance consisted in 100 parts 



52.38g.C.; 7.27g.H.; 22.68g.O.; 16.65g.N.; 1.02g.S. 



Of which were found in the urine. 9.406 2.663 14.099 16.28 1.02 



Of which were found in the feces. 1.471 0.212 0.889 0.37 



Retained ............... 41.50C; 4.40H; 7.69O; O.ON; O.OS. 



From this residue, with the taking up of 96.63 liters of oxygen, besides 39.6 

 grams water, 77.39 liters carbon dioxide were formed and the respiratory quotient 

 is therefore 0.801. Now 100 grams of such dry meat substance on complete 

 combustion yields 563.09 calories, and if we subtract the calorific value of the 

 corresponding urine (=113.70 calories) and feces (=17.76 calories), the sum, 

 131.46 calories, then 431.63 calories were set free in the body. For every gram 



A Q 1 AQ 



of nitrogen eliminated in the urine (16.28 gram) there is produced - 1g 00 =26.51 



iD.Zo 

 QA AQ 



calories; the corresponding quantity of oxygen is ' 00 =5.91 liter and the 



77 39 

 corresponding quantity of C0 2 produced is j^og =4< ^ ^ ters C0 2 . The calorific 



value for 1 liter of oxygen consumed is therefore - ' = 4.485 calories, and for 



1 liter of carbon dioxide produced . '. =5.579 calories. 



For milk protein ZUNTZ has calculated for 1 gram urea nitrogen 5.8 liters 

 oxygen, 4.6 liters carbon dioxide and 27 calories. The calorific value can be cal- 

 culated from this for 1 liter 0=4.66 and for 1 liter C0 2 = 5.87 calories. If we 



take the average of these calculations we obtain the calorific coefficients T ' =4.57 



Ij.Uz 



Cal 

 and rrvT = 6.73 for protein. 



For the three foodstuffs we have the following calorific values: 



Per 1 liter Relative Per 1 liter Relative 



Oxygen. value. Carbon dioxide. value. 



Protein ............ 4.57 100 5.73 113.4 



Fat ............... 4.69 102.6 6.63 131.3 



Carbohydrate ...... 5.05 110.5 5.05 100.0 



1 Zuntz, Loewy, Miiller and Caspar!, Hohenklima und Bergwanderungen, Berlin, 

 1906, pages 102, 103. 



