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NUTRITIVE VALUE OF GELATIN. 911
tion protein; the elimination of nitrogen was always somewhat increased.
On the fractional introduction <>f protein, Thomas 1
was nevertheless able
in dogs to produce nitrogenous equilibrium without essentially raising
the protein metabolism (in comparison with the starvation value). In
experiments upon himself he was not able to produce this.
It has been stated above that other foods may decrease the catab-
olism of proteins. Gelatin is such a food. Gelatin and the gelatin-formers
do not seem to be converted into protein in the body, and this last cannot
be entirely replaced by gelatin in the food. For example, if a dog is fed
on gelatin and fat, its body sustains a loss of proteins even when the
quantity of gelatin is great enough so that the animal with an amount of
fat and meat containing just the same quantity of nitrogen as the gelatin
in question, remains in nitrogenous equilibrium. On the other hand,
gelatin, as Voit, Panum and Oerum 2
have shown, has great value as
a means of sparing the proteins, and it may decrease the catabolism of
proteins to a still greater extent than fats and carbohydrates. This is
apparent from the following summary of Voit’s experiments upon a dog:
Food per Day. Flesh.
Meat. Gelatin. Fat. Sugar. Catabolized. On the Body.
400 200 450 -50
400 250 439 -39
400 200 356 +44
I. Munk 3
has later arrived at similar results by means of more deci-
sive experiments, and the recent investigations of Krummacher and
Kirchmann 4
show the extent of the sparing action of gelatin upon pro-
teins. The extent of protein destruction during gelatin feeding was com-
pared with the extent of protein catabolism in starvation, and it was
found that 35-37.5 per cent of the quantity of protein decomposed in
starvation could be spared by gelatin. The physiological availability
of gelatin was found by Krummacher to be equal to 3.88 calories for 1
gram, which corresponds to about 72.4 per cent of the energy-content of
the gelatin.
The value of gelatin has been found by Murlin 5
to be dependent to
a high degree upon the protein condition of the body, on the calorific
value of the food and the quantity of carbohydrates in the latter. If
in a man weighing 70 kilos, 51 calories per kilo were partaken, the quan-
tity of nitrogen eliminated wT
as 10 per cent more than the starvation
1
v. Hoesslin and Lesser, 1. c; Thomas, Arch. f. (Anat. u.) Physiol., Suppl. Bd.,1910.
- Voit, 1. c, 123; Panum and Oerum, Nord. Med. Arkiv., 11.
3
Pfluger’s Arch., 58.
4
Krummacher, Zeitschr. f. Biologie, 42; Kirchmann, ibid., 40.
* Amer. Journ. of Physiol., 19.
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