NUTRITION OF CARNIVOROUS ANIMALS. 
1 55 
tion sufficient for the metamorphosis of an adequate amount 
of tissue, that enough carbon and hydrogen may be set free 
for the support of the respiratory process. And we see a cor¬ 
responding activity in the Human hunters of the swift-footed 
antelope and agile deer, which answers a similar purpose; and 
which is remarkably contrasted with the stupid inertness of 
the inhabitants of the frigid zone, that is only occasionally 
interrupted by the necessity of securing the supplies of food 
afforded by the massive tenants of their seas. 
161. The nutrition of the Carnivorous races may, then, be 
thus described. The bodies of the animals upon which they 
feed, contain flesh, fat, &c., in nearly the same proportion as 
their own; and all, or nearly all, the aliment they consume, 
goes to supply the waste in the fabric of their own bodies, 
being converted into its various forms of tissue. After having 
remained in this condition for a certain time, varying ac¬ 
cording to the use that is made of them, these tissues un¬ 
dergo another metamorphosis, which ends in restoring them 
to the condition of inorganic matter; and thus give back to 
the mineral world the materials which were drawn from it by 
plants. Of these materials, part are burned off, as it were, 
within the body, by union with the oxygen of the air taken 
in through the lungs, from which organs they are discharged 
in the form of carbonic acid and water : the remainder are 
carried off in the liquid form by other channels. Hence 
we may briefly express the destination of their food in the 
following manner :— 
Carbonic acid and 
water, thrown off 
by respiration. 
Urea and biliary 
matter, &c., 
thrown off by 
other excretions. 
162. But in regard to the Herbivorous animals, the case 
is different. They perspire much more abundantly, and their 
temperature is thus continually kept down (§ 372). They 
consequently require a more active combustion, to de¬ 
velop sufficient bodily heat ; and the materials for this are 
supplied, as we have seen, by the non-azotized constituents of 
their food, rather than by the metamorphosis of their own 
tissues, which takes place with much less rapidity than in 
the carnivorous tribes. Hence we may thus express the 
Food consisting 'v 
of albuminous I 
and other com- { 
pounds J 
converted 
into 
r Living } 
< organised \ 
( tissue, j 
and this 
metamorphosed 
into 
