MUSCLES OK THE INSIDE OF THE SHotrLLER. 
937 
MUSCLES ON THE INSIDE OF THE SHOULDER. 
PLATE VI. Fig. 2. 
a. The flexor of the -arm, which is one of the most powerful of 
the flexor muscles., It has its origin in the extremity of the 
ridge of the shoulder-blade, in the form of a large and round 
tendon, which extends between two prominences in the upper 
portion of the front of the lower bone of the scapula. This 
groove, or pulley, is as perfect as it is possible to suppose it; 
and is lined with smooth cartilage, between which and the 
tendon there is interposed an oily fluid, which enables the 
tendon to move in this pulley without the danger of being 
injured by friction. Passing on from this pulley, and extend¬ 
ing beyond the head of the lower bone of the shoulder, the 
cord spreads out into a round fleshy substance, containing 
numerous tendinous fibres. It is deeply seated, and gives that 
fine fulness to the front of the arm. It is inserted into the head 
and neck of the bone of the arm, as also into the capsular 
ligament of the elbow-joint. It is the chief muscle, by which 
nearly the entire of the leg below the arm is bent. 
t>, b This muscle is called the pectoralis transversus , or the muscle 
which crosses the breast. It takes its rise from the first four 
bones of the chest, and, stretching across to the inner part of 
the arm, is inserted into the tendinous substance which covers 
the muscles of the fore arm, and extending a considerable way 
down the arm. Its use is to bind the arm to the side of the 
horse, and it also keeps the legs straight before the horse when 
it is at speed, so that the weight of the body may be received 
on them in a direction most easy and safe to the horse as well 
as the rider, and most advantageous for the full action of all 
the muscles connected with progression, 
c. This represents the disease called capped hock , or an enlarge¬ 
ment of the joint of the elbow, as described at page 131 
g. The internal flexor. It takes its rise from the inner head of 
the lower bone of the shoulder, and is inserted into the head 
of the inner splint-bone. Its office is to bend the leg, and to 
turn it very slightly. 
r. The principal veins, nerves, ana arteries of the shoulder and arm. 
Q 
