OSTEOLOGY AND ARTHROLOGY 59 



than the supraspinous. The spinal border is surmounted 

 by the cartilage of prolongation, the superior margin of 

 which is convex ; this cartilage extends posteriorly beyond 

 the posterior (axillary) border of the bone. 



The small tuberosity of the superior extremity of the 

 humerus is but slightly developed ; the great tuberosity, on 

 the contrary, is very large. The bicipital groove is situated 

 internal to this. The deltoid impression is scarcely marked. 



The forearm is short, directed obliquely downwards and 

 inwards, thus forming with the hand an angle, of which the 

 apex is directed inwards. The two bones of the forearm 

 are strongly bound to one another by an interosseous liga- 

 ment, which is formed of very short fibres. The radius 

 appropriates, at its superior extremity, the coronoid 

 process of the ulna. The latter is, notwithstanding, well 

 developed in the rest of its extent ; it has a flattened 

 shaft which almost completely overlaps the posterior 

 surface of the radius ; its inferior extremity reaches to the 

 carpus. 



The carpus is formed of eight bones — four in the superior 

 row, and four in the inferior. The third bone of the 

 superior row (cuneiform) is more in contact with the ulna 

 than with the radius. 



There are but four metacarpal bones ; there is no meta- 

 carpal of the thumb. The two median metacarpal bones 

 are the longest ; they are those which correspond to the 

 digits which alone touch the ground. The internal digit 

 and the external one are thin and short ; they are function- 

 less, as a rule, taking no part in supporting the limbs on 

 the ground. Notwithstanding this, they are formed, as 

 the other digits, of a number of phalanges, which give 

 them the semblance of perfect digits. (We shall soon see 

 that in certain animals there exist digits which, being in- 

 complete with regard to the numbers of their constituent 

 bones, more accurately merit the name of imperfect 

 digits.) 



The third phalanges are each enclosed in a horny hoof, 

 to which the name of onglon has been given. 



We have alreadv drawn attention to the smaller lateral 



