THE UTILIZATION OF ENERGY. 449 
Gain Over Fasting 
Metabolizable Metabolism. 
Energy of Total Gain 
Food, als. | 
Cals. Total Per Cent. of 
Cals.” ta 
Nothing .......... 0 —944 
HAG acai av excels oss Mee 1549 +540 1484 95.8 
Carbohydrates... ... 1549 +509 1453 93.8 
1549 +418 1362 87.9 
Meat ........... 1463 +332 1276 87.2 
! 2181 +805 1749 80.2 
Experiments by Gruber * upon the formation of fat from pro- 
teids (see p. 112) afforded the following results, computed ¢ by 
the use of the factors given on p. 414: 
Gain Over Fasting 
Metabolizable Metabolism. 
Energy of Total Gain 
Cals Cals. Total Per Ceat. of 
Cals. eee of 
Nothing .......... 0 —743 
1500 grms meat: 
Ist series...... 1325 250 993 74.9 
2d series...... 1325 296 1039 78.4 
Average ........ 1325 273 1016 76. 
The difficulty in interpreting these results, as well as those tabu- 
lated on p. 428, as already stated, lies in our imperfect data regard- 
ing the net availability of the materials below the point of mainte- 
nance. Rubner, in discussing his results, assumes an availability 
of 100 per cent., or in other words that the fasting metabolism is 
the measure of the amount of metabolizable energy required for 
maintenance. He accordingly subtracts this amount from the 
total metabolizable energy of the food and regards the remainder 
as excess food, which may be utilized for the storage of energy. 
The percentage utilization of this excess was as shown in the follow- 
ing table, to which Gruber’s results, computed by the writer in the 
same way, have been added: 
* Zeit f Biol, 42, 409. 
+ From the last two complete days of each series 
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