MUSCLES OF THE OUTSIDE OF THE SHOULDER. 
235 
and extends the arm or humerus upon the scapula, and moves 
it forward 
See the description at b. 
k. The posted spinatus muscle, situated behind the spine or ridge, 
and occupying the space called the fossa postea spinata. It 
extends to the lower bone of the shoulder,- and is inserted into 
the upper head of that bone. It is of a triangular form, and is 
flattened, and broader, but not so thick in substance as the 
antea spinatus muscle. It assists the flection of the hume¬ 
rus, and at the same time rolls it outwards. This is the 
tendon of the long extensor of the arm, which reaches from 
the upper angle and the posterior border of the scapula, to the 
point of the elbow and the inside of the arm. This muscle is 
a very important one. 
, t , Are the three divisions of another muscle concerned in the 
same office with p> arising from the shoulder-blade and the 
lower bone of the shoulder, and likewise attached to the point 
of the elbow by a very powerful tendon. 
t This is the middle flexor, which is one of the numerous and 
powerful muscles which bend the leg. It is also represented 
at e, plate vi. fig. 2, and is the muscle which bends the shank- 
bone, because it is situated precisely in the middle of the back 
part of the arm. It has its origin from the inner head of the 
lower bone of the shoulder, and is inserted into one of the 
bones on the inner side of the knee. The other is seen at 2, 
fig. 1, and is called the external flexor of the leg, in conse¬ 
quence of lying on the outer side of the arm, towards the 
back. It is inserted on the outer head of the lower bone of 
the shoulder; advancing towards the knee, it is tendinous ; and 
the tendon divides into two portions, one of which is inserted 
into the same bone of the knee, and the other into the outer 
small bone of the leg. The internal flexor is exhibited at g , 
plate vi. fig. 2. 
u. This is one of the muscles of the lower bone of the shoulder. 
It is the external one, whose office is to bend the arm. It 
arises from the inner and back part of the neck and body of 
the lower bone of the shoulder, and turns obliquely round it, 
and is inserted into the inner and upper part of the bone of 
the arm. 
