150 



THE STRUCTURE OF THE HORSE 



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

 with the processes much less developed, the acromion 

 especially, so prominent a feature in the scapula of man, 

 being scarcely visible. 1 There is no trace of a clavicle. 

 The scapula and the limb attached to it are not in any 

 way joined to the rest of the skeleton by bone, but only by 

 the muscles which pass from one to the other. The trunk 

 is, in fact, only slung between the two shoulder-bones. 



These differences are entirely related to the different 

 use and motions of the fore limb in man and the 

 horse respectively. In man the humerus moves at the 

 shoulder-joint in every direction. It can be swung 

 round so that its outer end forms a complete circle. The 

 muscles by which these actions are performed 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 provided 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 



1 Wincza has recently shown that in the early embryonic condi- 

 tion of the scapula of the horse this process is relatively much 

 larger than in the adult. This is in conformit}- with the general 

 law that the young show the more generalised, anc 1 the old the 

 more specialised, condition. He was unable to detect any sign of a 

 clavicle. 'Morpholep. Jahrb. Bd. xvi. (1890), p. 647. 



