THE LIMBS 



151 



motion. The fore limbs are never crossed forwards 

 across the chest, or thrown upwards behind the back, as 

 with our arms, and hence there is no necessity for a 

 clavicle, and the muscles which pass from the scapula 

 to the humerus, though present, are developed in a very 

 different degree. 



Corresponding w r ith the freedom and play of move- 

 ment of the human arm and hand, the first bone of the 

 limb proper, the humerus, in man is long and slender 

 and has a large globular upper extremity or i head,' 

 which plays freely in the shallow, cup-like (glenoid), 

 articular surface of the scapula, constituting a true ball- 

 and-socket joint. In the horse, on the other hand, the 

 humerus is comparatively short and stout, 1 and its 

 movements are extremely limited. It is, in fact, so short, 

 and placed so nearly horizontally, and so covered up 

 with muscles, that externally this segment makes no 

 distinct appearance, being buried in the body or trunk, 

 from which the limb only separates itself at the com- 

 mencement of the second segment or elbow-joint, instead 

 of at the shoulder, as in man. 



The skeleton of the second segment or forearm in man 

 consists of two bones placed side by side — (1) the ulna, 

 which is connected with the humerus by a simple hinge- 

 joint, allowing motion of bending (flexion) and straight- 



1 The actual length of the humerus of an average- sized horse and 

 man is almost identical, as seen in Frontispiece. 



