184 
LECTURES ON HORSES. 
necessarily have sustained. A third reason for placing the head 
of the os femoris in an angular position, and setting it off from the 
shaft or body of the bone by means of a neck — for so the inter- 
vening portion of bone is called — is, that the joints might possess 
an enlarged sphere of motion. In the fore extremity, the scalpula 
itself being a moveable bone, the humerus did not require this ; 
but in the hind, the pelvis being a fixture to the trunk, it was 
necessary to confer as much mobility upon the hip joint as was 
compatible with the strength required in it, to carry the weight of 
the body, and to guard against any risk of dislocation. Had any- 
thing like the force resulting from weight and action been in 
operation in the fore extremity the same as in the hind, the 
shoulder joint could never have admitted of the loose and super- 
ficial construction it at present, for the sake of motion, enjoys. It 
must have been furnished with the deep socket, and complete re- 
ception of the ball into it, which we observe in the articulation now 
under our consideration. 
A beautiful contrivance, however, in defence of dislocation, 
whether it be likely to happen from the extensive motion enjoyed 
by the hip joint, or from the resistance it opposes to the force of 
the weight and shocks it receives, is the round ligament, as it has 
been named ; a ligament or round cord, characteristically short 
and strong, one end of which is affixed to the centre of the spherical 
head of the os femoris, while its other end is rooted into the floor 
of the socket in which that head plays : thus in nowise interfering 
with the revolutions and turnings of the ball within its socket — in 
nowise limiting or abridging the movements of the hind limb, 
and yet most effectually, in all those varied movements, preserving 
the hip joint from dislocation. By the depth of the acetabulum, 
for so the socket in the pelvis is called — which in the recent sub- 
ject is still further deepened by an edging of cartilage or gristle, 
whose flexibility admits of all the required latitude of motion ; by 
the round ligament ; and by the thick and powerful muscles by 
which it is on every side invested — is the hip joint preserved 
from displacement : indeed, without rupture or laceration of the 
round ligament it is impossible for dislocation to take place. 
Another remarkable feature in the os femoris is the huge ill- 
shapen projection proceeding from its upper and posterior part, 
which has got the name of greater trochanter , by way of dis- 
tinguishing it from a process much less in magnitude arising from 
the body of the bone. This protuberant portion of bone may be 
regarded in the light of an elbow, or a hock, or any other pro- 
jection whose use is to serve as a lever of the most favourable 
description, compatible with the situation it is in and to the muscles 
attached to it. Into the great trochanter are inserted those 
