innutritive a food as grass, we see that the
immense quantity required necessitates an enormous digestive system;
that the limbs, small in comparison with the body, are burdened by its
weight; that in carrying about this heavy body and digesting this
excessive quantity of food, much force is expended; and that, having but
little remaining, the creature is sluggish. Compare with the cow a
horse--an animal of nearly allied structure, but habituated to a more
concentrated diet. Here the body, and more especially its abdominal
region, bears a smaller ratio to the limbs; the powers are not taxed by
the support of such massive viscera, nor the digestion of so bulky a
food; and, as a consequence, there is greater locomotive energy and
considerable vivacity. If, again, we contrast the stolid inactivity of
the graminivorous sheep with the liveliness of the dog, subsisting on
flesh or farinaceous matters, or a mixture of the two, we see a
difference similar in kind, but still greater in degree. And after
walking through the Zoological Gardens, and noting the restlessness with
which the carnivorous animals pace up and down their cages, it needs but
to remember that none of the herbivorous animals habitually display this
superfluous energy, to see how clear is the relation between
concentration of food and degree of activity.

That these differences are not directly consequent on differences of
constitution, as some may argue; but are directly consequent on
differences in the food which the creatures are constituted to subsist
on; is proved by the fact, that they are observable between different
divisions of the same species. The varieties of the horse furnish an
illustration. Compare the big-bellied, inactive, spiritless cart-horse
with a racer or hunter, small in the flanks and full of energy; and then
call to mind how much less nutritive is the diet of the one than that of
the other. Or take the case of mankind. Australians, Bushmen, and others
of the lowest savages who live on roots and berries, varied by larvae of
insects and the like meagre fare, are comparatively puny in stature,
have large abdomens, soft and undeveloped muscles, and are quite unable
to cope with Europeans, either in a struggle or in prolonged exertion.
Count up the wild races who are well grown, strong and active, as the
Kaffirs, North-American Indians, and Patagonians, and you find them
large consumers of flesh. The ill-fed Hindoo goes down before the
Eng