THE PRINCIPLES OF ANIMAL NUTRITION. 
INTRODUCTION. 
Tue body of an animal, regarded from a chemical point of view, 
consists of an aggregate of a great variety of substances, of which 
water, protein, and the fats, with smaller amounts of certain 
carbohydrates, largely predominate. By far the greater portion of 
the substance of the body, aside from its water, consists of so- 
called “ organic” compounds; i.e., compounds of carbon with hydro- 
gen, oxygen, nitrogen, and, to a smaller extent, with sulphur and 
phosphorus. These compounds are in many cases very complex, 
and all of them have this in common, that they contain a con- 
siderable store of potential energy. 
It is through these complex “ organic” compounds that the phe- 
nomena of life are manifested. All forms of life with which we are 
acquainted are intimately associated with the conversion of com- 
plex into simpler compounds by a series of changes which, regarded 
as a whole, partake of the nature of oxidations. During this break- 
ing down and oxidation more or less of the potential energy of these 
compounds is liberated, and it is this liberation of energy which is 
the essential end and object of the whole process and which, if not 
synonymous with life itself, is the objective manifestation of life. 
This is equally true of the plant and the animal, although masked 
in the case of green plants by the synthetic activity of the chloro- 
phyl in the presence of light. The process is most manifest in the 
animal, however, both on account of the inability of the latter to 
utilize the radiant energy of the sun and on account of the greater 
intensity of the process itself. 
Setting aside for the moment any storing up of material, and 
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