MUSCLES ON INSIDE OF THE SHOULDER 207 



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 extending 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 fullness 

 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. 



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 elbow, or an en- 



largement of the joint of the elbow, as described at 

 page 87. 



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, and arteries of the shoulder 

 and arm. 



