THE UTILIZATION OF ENERGY. 509 
to increase the gaseous exchange, the total metabolism being sub- 
stantially proportional to the total mass (horse + load), but in.com- 
puting the work experiments the same rest values are used as for 
the preceding experiments; that is, the results include the work 
required to simply sustain the weight as well as that required to 
move it. Computing the results in the same manner as before the 
authors obtain for an average speed of 90.18 meters per minute 
the following results: 
Locomotion per Meter. 
Per kg. live weight ......... 0.5004 cal. = 0.2126 kgm. 
“© total mass.......... 0.3914 “ =0.1663 “ 
Ascent, 
Per kilogram-meter ........ 6.502 cals. = 2.7640 “ = 36.19% 
A comparison of these figures with those on p. 506 shows 
that for this animal a load of 127 kgs. caused about 8 per cent. 
increase in the energy expended, per kg. of total mass, in horizon- 
tal locomotion, but no increase in that expended per kilogram- 
meter in ascent. 
Work of Descent.—In descending a grade the force of gravity 
acts with instead of against the animal and tends therefore to 
diminish the metabolism. On the other hand, however, as the 
steepness of the grade increases the animal is obliged to put forth 
muscular exertions to prevent too rapid a descent, and this tends 
to increase the metabolism. It was found that an inclination of 
2° 52’ caused the maximum decrease in the metabolism. At 5° 45’ 
the metabolism was the same as at 0°, while on steeper grades it 
was greater than on a level surface. 
Work at A Tror.—A smaller number of experiments were made 
upon work at a trot under varying conditions. In trotting, the up 
and down motion of the body is much greater than in walking, while 
but a small part of the muscular energy thus expended is available 
for propulsion. It was therefore to be expected that the energy 
tequired for horizontal locomotion would be greater at a trot than 
at a walk, and the results of the experiments corresponded fully 
with this expectation, the computed energy per meter being found 
to be 
Per kg. live weight............-eeeeeeee 0.5660 cal. 
« « mass (horse+load)..........6-. 0.5478 “ 
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