490 EQUILIBRIUM OF ANIMALS :-BASE OF SUPPORT. 
which its feet cover and inclose between them; and the 
wider this space, in proportion to the height of the centre of 
gravity, the more stable will the equilibrium be, since the 
body may be more displaced without being upset. Thus in 
fig. 231 the table a must be upset; because the line of direc¬ 
tion e from the centre of gravity c falls outside the base of 
support d; whilst the table h, although equally inclined, will 
not be upset but will return to its proper place, because the 
line of direction e from its centre of gravity c falls within its 
base d . Hence an animal which is supported upon four legs 
will stand much more firmly than one which rests on two 
only; since its real base is the whole space included between 
its four points of support. And again, an animal is more 
firm when standing upon two legs, than when resting upon 
one only. 
652. Moreover when an animal rests upon four legs, the 
extent of its base is but little influenced by the size of the 
feet; and thus to render them 
broad would be to increase 
their weight without adding 
much to their use as supports. 
This is easily understood by 
comparing a quadruped to a 
four-legged table ; if the legs 
are sufficiently strong to support 
the weight that rests upon 
them, it matters little in regard 
to the steadiness of the table, 
whether they bear upon the 
ground by mere points or by flat 
surfaces; since it is the large sur¬ 
face that would be enclosed by 
lines joining them, which consti¬ 
tutes the real base. Hence we 
find that, in most quadrupeds, 
the limbs only touch the ground 
Fig. 233. 
Foot of Horse. 
Fig. 232. 
Foot of Dees. 
by slightly-dilated extremities; and the number of fingers is 
reduced more and more, without diminishing their effect as 
instruments of locomotion. Thus in Ruminant animals, as 
the Deer, the number of toes is reduced to two in each foot, as 
seen in fig. 232, where t represents the tibia, ta the bones of 
