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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.
L.CO2 L.O2
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 J
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; 7.690; 0.0N; 0.0S.
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
of nitrogen eliminated in the urine (16.28 gram) there is produced - „ ~q =26.51.
calories; the corresponding quantity of oxygen is
’
n =5.91 liter O and the
77.39
corresponding quantity of C02 produced is ’„» =4.75 liters C02 . The calorific
cyo r -I
value for 1 liter of oxygen consumed is therefore _
Q
. = 4.485 calories, and for
1 liter of carbon dioxide produced ,
7C. = 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 C02 = 5.87 calories. If we
Cal.
take the average of these calculations we obtain the calorific coefficients T rt
’
=4.57
L/.U2
Cal.
and >
r<n
=5.73 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 .
1
Zuntz, Loewy, Miiller and Caspari, Hohenklima und Bergwanderungen, Berlin,
1906, pages 102, 103.
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