REVIEW—BRIDGEWATER TREATISES, NO. 5, &C. G19 
the fore extremity, and, consequently, if they had been disposed 
vertically in a straight line, they would have elevated the hinder 
part of the trunk to too great a height compared with the fore 
part. This is obviated by their forming alternate angles with 
one another. As the pelvis connects the spine with the joint of 
the hip, and even extends farther backwards, the thigh bone 
must necessarily be brought forwards ; then the tibia and fibula, 
which compose the bones of the leg, must be carried backwards 
to their junction with the bones of the foot; and, again, the 
foot must be turned forward in its whole length from the heel to 
the extremities of the toes. On comparing the position of the 
corresponding divisions of the anterior and posterior extiemities, 
we observe that they incline, when bent in opposite directions; 
for in the former we find, in following the series of bones from 
the spine, that the scapula proceeds forwards, the humerus 
backwards ; the radius and ulna again forwards, and the lower 
part backwards,—positions which are exactly the leveise of the 
corresponding bones of the hind limb. 
“ The weight of the body, in consequence of this alternate 
direction of the angles at the successive joints, must always tend, 
while the quadruped is on its legs, to bend each limb; a ten¬ 
dency which is required to be counteracted by the actions of the 
muscles which are situated on the external side of each of those 
angles. These muscles are the extensors of the joints, that is, 
the muscles which tend to bring their parts into a straight line. 
It is, in fact, by this muscular action, much more than by sim¬ 
ple rigidity, that the limb supports the superincumbent weight 
of the body. It is evident that greater muscular force is neces¬ 
sary for tins purpose when the joints are bent than when they 
are already extended; and the positions of the fore legs being 
naturally in this condition, require less power than those of the 
hind legs to retain them in their proper relative positions. 
“ The most complete instance of a vertical arrangement of the 
bones of the extremities is seen in the elephant, where, in order 
to sustain the enormous weight of the body, the limbs are shaped 
in four massive columns, of which the several bones are disposed 
nearly in perpendicular lines. By this means the body is sup¬ 
ported with scarcely any muscular effort, and the attitude of 
standing is, in this animal, a state of such complete icpose, that 
he often sleeps in that position. But in almost all other quadru¬ 
peds the mere act of standing, though a state of comparative 
rest, implies, for the reasons already given, a degiee of muscular 
exertion, and they can enjoy complete repose only by letting the 
body recline upon the ground. 
“ The conformation of the hind extremities, which, as we 
