26 LAMENESS IN THE HORSE. 



energy. The elbow joint is made immovable by the flexor 

 muscles and their aponeuroses. Lateral motion of all joints 

 below the elbow joint is inhibited by the shape of the 

 articular surfaces and the ligaments ; only the shoulder 

 joint forms an exception, as ligaments are here replaced by 

 the postea-spinatus muscle, flexor brachii, the large extensor 

 of the fore-arm, teres minor, the short abductor of the arm, 

 and, on the internal face, the wide and stroug tendon of the 

 subscapularis muscle and teres major. The elasticity of 

 these muscles and their aponeuroses fix the shoulder joint 

 sufficiently to prevent uudue lateral motion. 



The horse, as is well known, can" stand up for days 

 without getting tired, since all the joints of the supporting 

 leg can be fixed without the aid of muscular elements. 

 During movement this mechanism, fixing all joints while at 

 rest, has another important duty to perform, it receiving the 

 shock coming from the weight of the body, which the elastic 

 muscular elements could never stand. This inelastic 

 check-apparatus therefore prevents collapse of the whole 

 limb wdienever weight is thrown upon it, and consequently 

 the fibrous parts of the flexors, but never their muscular 

 portion, sustain injury from concussion. The forward 

 stride, — that is, the action of the swinging leg, — is partly 

 due to the weight of the foot, but mainly depends upon the 

 mastoido-humeralis, antea-spinatus, biceps brachii, and 

 coraco-humeralis muscles While these muscles advance 

 and extend the shoulder joint the elbow joint is flexed, this 

 greatly facilitating the forward motion of the leg. Thte 

 olecranian muscles extend the elbow joint ; at the sam:) 

 time they extend all joints below it, as the extensor muscles, 

 like the flexors, have fibrous cords running through them, 

 being also covered with aponeuroses. Whenever the elbow 



