METHODS OF INVESTIGATION. 245 
No. of Heat of Combus- 
Samples. tion per Gram, 
Cals. 
CACC vies wiaes watts tae Seth oe eo ertens wage Sash vee 4 5.6776 
Sheep's ccs giao niu Madea gece wa eee sae es 2 5.6387 
SWING as sicssan es Susy ewes Gwe cede seats wees 2 5.6758 
Ors yc ess vaatoaiae line ve sadetdeasieee: eased 3 5.5990 * 
FRAD BIG 5 ace ga canerareudeaceare aretha Naiore tani anda ea een ats 2 5.6166 
eR: ca ic ceca re tea eke cae Seine aseee a oes 2 5.6173 
human fat are given on p. 61, found for the heat of combustion of 
the same twelve samples values ranging from 9.474 Cals. to 9.561 
Cals. per gram, the average being 9.523 Cals. Other results are 
noted in the table on pp. 237-9. 
Determination of Kinetic Energy. 
Mechanical Work.—The energy of the mechanical work done 
by the animal upon its surroundings is derived, as was seen in Part 
I, immediately from body materials and mediately from the food, 
and is one of the two forms in which kinetic energy leaves the body. 
The energy of the mechanical work done by the animal may be 
measured in various ways, the consideration of which belongs 
to the domain of mechanics and lies outside the scope of the 
present work. In general two classes of appliances have been used: 
First, dynamometers proper, in which the work is expended in 
overcoming a known resistance, produced either by friction or by 
a magnetic field, the work done being measured by the tension of a 
spring or by the amount of electric energy produced. 
Second, the tread power, in which the work, aside from that of 
locomotion, consists in lifting the body vertically and is propor- 
tional to the product of the mass of the body into the distance 
through which it is raised. 
Heat.—The second form in which kinetic energy leaves the 
body is heat. In an animal doing no work all the energy arising 
from the metabolism in the body ultimately takes this form, and 
even when mechanical work is done the larger share of the outgo 
of kinetic energy consists of heat. Part of this heat is imparted to 
the surroundings of the animal by conduction and radiation and a 
* Contained an average of 3.65 per cent. glycogen. 
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