66 OSTEOLOGY. 



The carpus and tarsus bend or flex in opposite directions, but 

 below these joints the skeleton of the fore limb differs in no very 

 material point from that of the hinder one. 



PECTORAL ARCH. 



The 'pectoral arch or shoulder-girdle consists, in the horse, of 

 a bone called the scapula, on which we find a prominent object, 

 the coracoid apophysis. This process being developed from a 

 distinct ossific centre, is considered the homologue of the coracoid 

 bone, a bone which is greatly developed in some animals, 

 articulating, in some cases, with the sternum below. Another 

 bone that very frequently assists in the formation of the arch, the 

 clavicle or collar bone, is altogether absent in the horse, as in the 

 rest of the Ungulata. On the other hand, the pelvic or hinder 

 limb is firmly attached to the sacrum by means of the pelvic 

 arch, which is complete. 



PECTORAL OR FORE LIMB. 



Regarding the anterior extremity as consisting of the limb 

 and its incomplete arch, the bones we have to describe are 

 the scapula, humerus, radius, and ulna ; the carpus, consisting 

 of eight bones — viz., the cuneiform, lunar, scaphoid, and trapezium 

 in the upper row, and the unciform, magnum, trapezoid, and 

 pisiform in the lower row ; three metacarpal bones, two of which 

 are imperfect ; three sesamoid bones, one pair and a single one, 

 the latter called also the navicular bone : and finally, three 

 phalanges or finger bones, called respectively the os sufiraginis, 

 OS coronae. and os pedis. 



SCAPULA. 



(PL. L J.) 



The scapula is a flat bone situated on the antero-Iateral 

 surface of the thorax, with its long axis sloping downwards and 

 forwards ; it is triangTilar in shape, the base being turned up- 

 wards. In the horse this bone is strong but comparatively small ; 

 it is broad and thin superiorly, becoming both narrower and 

 thicker inferiorly ; its position, or rather slope, is a point of 

 importance in the conformation of the animal, and varies to some 



