398 



THE COMPLETE GRAZIER. 



above and a cartilaginous part below. Of the 18 pairs of ribs, the 

 costal cartilages of the first eight pairs have a separate and independent 

 attachment with the sternum ; these are called true or sternal ribs. 

 Of the remaining ten the cartilages become more or less confluent, and 

 reach the sternum, if at all, collectively ; these, therefore, are called 

 false or asternal ribs. The length of the ribs increases from the first 

 to the ninth, then diminishes. The width increases from the first to 

 the sixth, then diminishes. The curve of each rib is shorter and more 

 pronounced, the farther the rib is from the head of the horse. The 

 mobility of the ribs is hardly perceptible in the first pair ; it increases 

 to the ninth or tenth, then diminishes. 

 The pectoral arch, or shoulder girdle, consists of a pair of scapulae, 



Fig. 90. Skeleton of the Horse. 



or shoulder blades, one on each side. There are no clavicles, or collar 

 bones. The scapula is long, slender, and has a ridge only slightly 

 developed. As, however, this ridge is thickened and turned backwards 

 somewhat above the middle, there is no difficulty in determining 

 whether a dry scapula is right or left. The upper free margin of the 

 scapula is bordered by a cartilage (the supra-scapular cartilage), which 

 becomes ossified in old horses. 



The upper end of the humerus, or shoulder bone, articulates with 

 the glenoid cavity at the lower extremity of the scapula. Inferiorly, 

 the humerus articulates with the radius. 



Of the two bones radius and ulna which make up the typical fore- 

 arm in vertebrate animals, the radius alone is well developed in the 

 horse, the ulna being represented only by its upper part, which is 



