ANATOMY OF THE HORSE. 
428 
faces in front, which, like the cavity behind, occasionally receive 
processes of the bone below. 
Connexion, —The head of the humerus is ad^ipted to the glenoid 
cavity of the scapula; the condyles are fitted into concavities upon 
the upper extremity of the radius. 
Development .— In the young bone, the head, condyles, and 
tubercles are epiphyses. 
OF THE ARM. 
The arm is composed of a single bone, the os brachiiy which 
corresponds to the human radius and ulna united together. 
ARM-BONE (os BRACHII.) 
Form. —Cylindroid; flattened before and behind ; slightly 
curved forwards. 
Division. —Into radial and ulnar portions. 
The RADIAL PORTION consists of^a body and superior and 
inferior extremities. 
The body is long; prominent and smooth anteriorly; slightly 
excavated and roughened posteriorly, where it is pierced in a 
direction downward by the medullary foramen: the former is 
clothed by the extensor muscles of the leg and foot; the latter by 
the flexors of those parts. 
The superior extremityy like the inferior, expanded into greater 
‘.breadth than the body, presents an articulatoiy surface, divided, 
by a gentle eminence running across the middle, into two concavi¬ 
ties, of which the inner is broader and nearer circular than the 
outer; the latter, indeed, has a superficial rising, taking the 
direction which makes a similar but imperfect subdivision of it : 
.these concavities receive the condyles of the humerus. The exter¬ 
nal lateral process is more prominent and sharper than the inter¬ 
nal, and is surmounted in front by a small tubercular eminence: 
to these processes the lateral ligaments are attached ; the eminence 
serves also to deepen the outer cup of articulation. 
The infer'ior extremity is remarkable for the number and variety 
of its articulatory surfaces, and for presenting a hiatus extero- 
posteriorly, as if a piece of the bone had been chiselled out. It 
possesses three articulatory surfaces. The largest, or inner one, 
is quadrilateral in outline, sigmoid in superficies; the middle is 
similar in form, but of smaller dimensions; the outer, or smallest, 
is an ovoid convexity. The internal lateral process is the most 
prominent; the external has a groove along it. The bone is also 
grooved in front by the passage of the extensor tendons. 
