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CALORIC VALUES OF FOOD-STUFFS. 885
calculate the part taken by the fats and carbohydrate will be shown in connection
with the calculation of the energy metabolism.
The quantity of water and mineral bodies voided with the urine and
feces can easily be determined. The quantity of wr
ater eliminated by
the skin and lungs may be directly estimated by means of the large
respiration apparatus.
The organic constituents of the body as well as the foodstuffs intro-
duced, represent a sum of chemical’ energy which the body can use
for force. The exchange of material is also an exchange of force,
and the first stands in such close relation to the second that the study
of one cannot be separated from the other. The energy theory of
metabolism has exercised an extraordinarily fruitful influence upon
the entire study of metabolism and nutrition, and this is due in great
measure to the work of Rubner.
This energy of the various foods may be represented by the amount
of heat which is set free in their combustion. This quantity of heat is
expressed as calories, and a small calorie is the quantity of heat necessary
to warm 1 gram of water from 0° to 1° C. A large calorie is the quantity
of heat necessary to warm 1 kilo of water 1° C. Here and in the follow-
ing pages large calories are to be understood. There are numerous
investigations by different experimenters, such as Frankland, Dan-
ilewski, Rubner, Berthelot, Stohmann, Benedict and Osborne,
and others, on the calorific value of different foodstuffs. The following
results, which represent the calorific value of a few nutritive bodies on
complete combustion outside of the body to the highest oxidation prod-
ucts, are taken from Stohmann’s 1
work.
Calories.
Casein 5 . 86
Ovalbumin 5 . 74
Conglut in 5 . 48
Protein (average) 5.71
Animal tissue-fat 9 . 50
Butter-fat 9 . 23
Cane-sugar 3 . 96
Milk-sugar 3 . 95
Glucose 3 . 74
Starch 4 . 19
Fats and carbohydrates are completely burnt in the body, and one can
therefore consider their combustion equivalent as a measure of the living
force developed by them within the organism. We generally designate
9.3 and 4.1 calories for each gram of substance as the average for the
physiological calorific value of fats and carbohydrates respectively.
1
See Rubner, Zeitschr. f. Biologic, 21, which also cites the works of Frankland
and Danilewski; see also Berthelot, Compt. Rend., 102, 104, and 110; Stohmann,
Zritschr. f. Biologie, 31; Benedict and Osborne (vegetable proteins), Journ. of biol.
Chem., 3.
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