LECTURE III 

 FRONT LIMB 



This limb is composed of 20 bones, and includes the shoulder, 

 arm, forearm, and foot. 



Shoulder. — The shoulder contains but one bone, the scapula, 

 or shoulder blade. This is triangular and situated at the 

 front portion of the chest wall. Its direction is downward 

 and forward, and it articulates below with the head of the 

 humerus, or arm bone. The inner surface is somewhat concave. 

 The external surface is divided into two portions by a long 

 ridge which extends lengthwise of the bone. The upper portion 

 is flat and thin. 



Arm. — The arm contains a single long bone, the humerus. Its 

 upper end articulates with the scapula, and the lower end with 

 the ulna and radius. It offers for description a shaft and upper 

 and lower extremities. A peculiar feature of the shaft is a sort 

 of furrow, which twists partially around the bone and is known 

 in anatomy as the furrow of torsion. The superior extremity 

 shows a rounded head, which is fitted for articulation with a 

 corresponding cavity* of the scapula, and the bicipital groove 

 in front, which holds the tendon of the biceps muscle. 



The inferior extremity is flattened. Its articular surface has 

 two condyles, separated by a shallow groove, fitting it for artic- 

 ulation with the radius. This extremity shows, on its posterior 

 surface, a deep fossa which fits the peculiar articular surface 

 of the ulna and gives a perfect hinge joint that is not easily 

 dislocated. 



Forearm. — The forearm contains two bones, the radius and 

 ulna. In the horse and cow these are firmly united. The radius 

 belongs to the group classified as long bones, and articulates 

 with the humerus above and the carpal bones below. Its an- 

 terior surface is convex and smooth; its posterior surface, con- 

 cave. The ulna is also a long bone, located just back of the 

 radius. The shaft is triangular. The upper extremity shows a 

 marked enlargement which is useful for attachment of muscles 



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