THE UTILIZATION OF ENERGY. 521 
Work per 
Gram, Car. 
bon Dioxide 
No. 1—Climbing a hill det tials cdc lauce. geek bate ee aes sal ds bee 215.18 
18 days later ........... ccc ceecaeecoes 306.18 
Hurst tial sede a8ded das eee cs a biask oe 182.70 
2 days after first trial................... 248 .34 
IO: 8 BE EES gL lone aan ae cbs aoa 253.74 
No. 2—Treadmill....} 12 “ “ Oe * Eades ean athee arith 238.85 
14“ “f BE weidrase cate areeass asepauene: ls 210.87 
169 “« PhS ee Savoie haa e aveldeed, 227 .04 
Bi Ne a aise eu BON BO 
24 months after first trial........ Boren 441.17 
First trial sco. c0dv. cesses boda bed ed eco 231.24 
No. 3—Treadmill .... ) 2 days after first trial..................... 231.24 
4 « ef BE ONES atbial aad te lev Sie ee wees ak 286.25 
In walking the same distance (468 M.) No. 1 excreted the following 
excess of carbon dioxide over the rest value: 
Firsttnal codes ese tewheweeaees 4.505 grams 
A week later................0. eee 3.690 “ 
A month later..............0....0... 2.780 “ 
It appears from these results that the gradual strengthening of the 
muscles during convalescence results in a more economical per- 
formance of their work, largely independent of any special training 
for a particular kind of work. It seems a justifiable conclusion, 
therefore, that a part of the gain due to training arises from its 
direct effect in strengthening the muscles, as well as from the in- 
creased skill acquired in their use. Conversely, the effect of fatigue 
in increasing the relative metabolism, as shown by Loewy,* would 
seem to be in part a direct effect. Schnyder summarizes the matter 
in the statement that it is not the work itself, but the muscular 
effort required, which determines the amount of metabolism. 
In the case of domestic animals kept chiefly for work, however, 
we may safely assume that they are constantly in a state of training, 
and that the results obtained by Zuntz and his associates on the 
horse are applicable to work done by normal animals within the 
limits of the experimental conditions. 
* Arch. ges. Physiol., 49, 405. 
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