336 THE HORSE. 
on itself. In the upper part it is expanded laterally to form the external 
tuberosity (5, Fig. 24) on the outside and the scabrous tubercle (4, Fig. 25) 
internally, both being for the attachment of muscles. ‘Towards the lower 
extremity it becomes rounded, and then suddenly spreads out to present 
the wide surface which ends in the condyles on each side with the inter- 
vening articular surfaces. 
THE SUPERIOR EXTREMITY, larger than the inferior, presents for con- 
sideration a head and four tubercles. The head is the hemispherical 
smooth part, projecting posteriorly. It articulates with the glenoid 
cavity of the scapula, which it much exceeds in extent of superficies. 
Anteriorly, the head is surmounted by four tubercles, three, directly 
in front, are between two smooth grooves, which are covered with 
cartilage. The outer, or fourth tubercle, is joined with the tuberosities 
by a protuberant ridge, the external edge of which serves to guard 
against dislocation. 
THE INFERIOR EXTREMITY is made up of two condyles, or knuckle-like 
projections (s, 9, Fig. 24), having between them the smooth articular sur- 
face for the elbow joint. This surface is broad, and assumes a segmental 
form, being divided into three portions by projecting lines,—1st, a middle 
Fia. 24.—ExTERNAL View oF Lert HumEnvs’ 
1. Body of humerus with musculo-spiral groove. 6. Sigmoid fossa. 
2. Head. 7. Olecranon fossa. 
3. External tubercle. 8. External condyle. 
4. Tubercles in front of hea? 9. Internal condyle. 
5. External tuberosity. 
groove, which terminates in front in the coronoid fossa and behind in the 
olecranon fossa, each being for the reception of the corresponding pro- 
cesses of the ulna and radius, thereby checking the motion of tho joint ; 
2d, the external groove, which is comparatively slightly marked ; and 3d, 
the smooth surface lining the internal condyle. All of these fit accu- 
rately into the articular surface of the ulna and radius, to be presently 
described, allowing of nothing but a hinge-like motion. Of the condyles, 
the inner is larger and more projecting than the outer. 
