THE LIMBS. 1G1 



formed require for their attachment outstanding 

 ridges on the scapula. This bone, moreover, requires 

 to have a certain degree of fixity, especially provision 

 against its being driven too far inwards or outwards 

 during the lateral action of the arms. This is pro- 

 vided for by its being connected to the sternum by 

 the intervention of the clavicle. In the horse there 

 is practically but one action at the shoulder, and 

 that not a very extensive one — a fore-and-aft hinge 

 scapula is a very much simpler bone, long, narrow, 

 flat, with the processes much less developed, the 

 acromion 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 with the freedom and play of 

 movement 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 

 " head," which plays freely in the shallow, cup-like 

 (glenoid), articular surface of the scapula, constitut- 

 ing a true ball-and-socket joint. In the horse, on the 

 other hand, the humerus is comparatively short and 

 stout,* and its movements are extremely limited. It 



* The actual length of the humerus of an average-sized 

 horse and man is almost identical, as seen in Frontispiece. 



