160 THE STRUCTURE OF THE HORSE. 



or "true shoulder-bone/' or "blade-bone" (which is 

 itself composed in infancy, and in some animals per- 

 manently, of two separate bones, the scapula proper 

 and the coracoid), and the clavicle or " collar-bone/' 

 a strong curved bar, united at its outer end with the 

 scapula, and at its inner end with the sternum or 

 breast-bone. The scapula is of complex shape, with 

 strong projecting processes. In the horse (see Fron- 

 tispiece) the humerus especially, so prominent a fea- 

 ture in the scapula of man, being scarcely visible.* 

 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 differ- 

 ent 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 per- 



* Wineza has recently shown that in the early embryonic 

 condition of the scapula of the horse this process is relatively 

 much larger than in the adult. This is in conformity with 

 the general law that the young show the more generalized, 

 and the old the more specialized condition. He was unable 

 to detect any sign of a clavicle. Morphdhg. Jahrb. Bd. xvi. 

 (1890), p. 647. 



