OSTEOLOGY. 



the arciform ligaments attached, and the 'posterior border, concave 

 and round, gives attachment to muscles. 



The distal extremity is pointed, and extends a little below the 

 middle of the radius, though sometimes, in the ass and mule par- 

 ticularly, it reacbes the inferior extremity of that bone. 



The proximal extremity comprises that 

 considerable portion of the bone, corres- 

 ponding to the elbow of man, which projects 

 upwards and backwards from the articular 

 surface of the radius, and is known as the 

 olecranon process. It presents two sur- 

 faces, two borders, and a summit. The 

 external surface is slightly convex, and 

 roughened for muscular attachment ; the 

 internal surface is hollowed and smooth ; 

 the j)Osterior border, concave, thin, and 

 smooth ; and the anterior border, thin 

 superiorly, is hollowed into a crescent- 

 shaped surface, which articulates Avith, or 

 rather behind and between, the condyles of 

 the humerus, the prominent portion being 

 known as the beah of the olecranon. The 

 summit is the broad roughened protuberance 

 which gives insertion to the tendon of the 

 triceps extensor brachii muscle, the olecranon 

 being the lever on which that muscle acts. 

 It is important to note that the develop- 

 ment of the ulna is directly proportional to 

 the number of fingers or digits, hence the 

 horse, being a monodactyle, has a very short 

 ulna ; compare this bone in the ox and dog\ 



Frr.. 16. 

 I'ront aspect of the right 

 carpus of a Horse. 1, Cunei- 

 form ; 2, Lunar ; 3, Scaphoid ; 

 4, Trapezium ; 5, Unciform ; 

 6, Magnum ; 7, Trapezoid ; 

 * *, Small metacarpals, the 

 large one lying between and 

 before them. The uppermost 

 bone is the distal end of the 

 radius. 



The carpus, wrist, or hnee, as it is incorrectly termed in 

 quadrupeds, is composed of seven and often of eight small, 

 irregular bones, arranged in two rows of three each, one above 

 the other, the seventh being at the back of the three in the upper 

 row, and the eighth, when present, in a similar position with 

 respect to the lower row. The joints between them pass com- 

 pletely through from front to back, and are so arranged that those 



