256 PRINCIPLES OF ANIMAL NUTRITION. 
Income Outgo, 
Cals. Cals. 
HO0d ees oxvia sau eae x ness Gee eases Sek ees 32,177 .3 
HOCESE s5SA ba Mey iaus ues Mae cA a Scene,  >-gheeueas 11,750.3 
UNINE 22 is nA0d Soa oa Aan weeny hel Wael) jeden wads 1,945.0 
Methane <iccceescaen ce awcan aes Seaucieaian|  gykenueece 2,113.7 
Proteinygained 54 a dwcen sce ogee sais ben ewwae|) a eeeles 211.2 
Fat OE Ot creat all geek aed ed eae ana h —aee ches g 1,337 .6 
Balance: jicsacncneeacciew ss aces eet eee  acdevets 14,819.5 
32,177 .3 32,177 .3 
ment, this is the most accurate method available for determining 
the heat production of an animal during a considerable period of 
time. To short periods it is inapplicable for obvious reasons. 
Heat Propuction aND Heat Emissron.—In conclusion, it is 
important to remember that what is determined more or less accu- 
rately by all these indirect methods is the amount of energy which 
takes the kinetic form, and in the absence of mechanical work 
finally appears as heat. In other words, what is determined is the 
heat production by the animal. On the other hand, the results ob- 
tained with an animal calorimeter show the amount of heat given 
off by the animal during the experiment, that is, the heat emission. 
But these two, heat production and heat emission, are by no means 
necessarily equal. On the one hand, heat produced may be tem- 
porarily stored in the body, or, on the other hand, heat retained in 
the body from a previous period may be given off along with that 
actually produced during the experiment. 
' This is sufficiently obvious in case of changes in the body tem- 
perature, but even when the latter remains constant the possibility 
of a temporary storage of the materials of the food, and especially 
of water, in the body, must be considered. If, for example, the con- 
sumption of water in an experiment exceeds the total amount given 
off in the visible and gaseous excreta, the quantity of heat required 
to warm the excess of water to the temperature of the body remains 
in the animal as sensible heat. The heat is produced but not 
emitted. If, on the other hand, the excretion of water exceeds the 
consumption, sensible heat is removed from the body in this excess 
and the emission of heat exceeds the production by a corresponding 
amount. What is true of water is of course true also, ceteris paribus, 
of the total income and outgo of matter, although the water, on 
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