EQUILIBRIUM OF ANIMALS :—BASE OF suPPoRT. 491 
ie tarsus, c the bone of the metatarsus termed the canon (in 
hich the trace of a division into two pieces can be seen), 
and p, pi, pt, the three phalanges of the toes, of which the 
st is enveloped in the hoof, which is nothing else than a 
ge nail inclosing the whole extremity of the toe. In the 
Horse this consolidation is carried still further than in the 
wuminants, for it has only one toe in each foot (fig. 233); but 
e see the rudiment of an additional bone in the metatarsus 
b, hich 3 is commonly termed the splint bone. 
‘ pes: But when an animal is supported upon two feet only, 
whatever may be their degree of separation from each other, 
Biheso of support cannot have sufficient extent, unless the 
emities touch the ground by a considerable surface. This 
3 S the case with the foot of Man, and still more with that of 
many Birds which habitually stand 
ppon one leg (fig. 234). In order 
tat an animal may hold itself in 
equilibrium upon a single limb, it 
is necessary that the foot should 
ye placed vertically beneath the 
sentre of gravity of the body; 
md that its muscles should be so 
mranged as to permit it to keep 
hb s limb inflexible and immov- 
abl e. Man can accomplish this, 
gr the centre of gravity of his 
ody is at- about the middle of the 
alvis ; and to place this vertically 
V one foot, it is sufficient for 
im to bend himself a little from 
ae side which is not supported. 
at the greater number of Qua- 
rupeds are destitute of the power ; 
f doing this; and a large part , 
# them cannot even raise them- 
es on their hind legs, on 
ecount of the direction of these members dieesls to the 
a k; or if they can do so for an instant, they cannot 
intain themselves in this position. The reason of this is 
ry simple. The base of support, on account of the small- 
ss of the feet, is very narrow, and the centre of gravity of _ 
