The =intercornual articulation= is an amphiarthrosis formed by the junction of the distal extremity of the great cornu with the proximal end of the small cornu (kerato-hyal). They are united by a very short piece of cartilage, in which there is usually a small nodule of bone in the young subject. This nodule, the epihyal or middle cornu, is usually fused with the great cornu in the adult. The chief movement here is also hinge-like, the angle between the cornua being increased or diminished. The =basi-cornual articulation= is a diarthrosis formed by the junction of each small cornu (kerato-hyal) with the body (basi-hyal). The small cornu has a concave facet which articulates with the convex facet on either end of the dorsal surface of the body. The capsule is ample enough to allow considerable movement, which is chiefly hinge-like. The movements of the hyoid bone are concerned chiefly in the acts of mastication and swallowing. In the latter the distal parts of the hyoid bone are moved forward and upward, carrying the root of the tongue and the larynx with them, and then return to their former position. THE ARTICULATIONS OF THE THORACIC LIMB In the absence of the clavicle the thoracic limb forms no articulation with the trunk, unless we regard as such the union by muscles. The movement of the shoulder on the chest-wall is chiefly rotation around a transverse axis passing through the scapula behind the upper part of the spine. THE SHOULDER JOINT The shoulder or scapulo-humeral joint (Articulatio scapulo-humeralis) is formed by the junction of the distal end of the scapula with the proximal end of the humerus. The =articular surfaces= are: (1) On the scapula, the glenoid cavity; (2) on the humerus, the head. Both surfaces are approximately spherical and similar in curvature, but the humeral surface is much more extensive than that of the scapula. The =joint capsule= is ample enough to allow the bones to be drawn apart about an inch (ca. 2 to 3 cm.); but this requires a very considerable amount of force unless air is admitted into the joint cavity. The fibrous layer (or capsular ligament) is not attached to the margin of the joint surfaces, but at a distance of one to two centimeters from it. It is strengthened in front by two diverging elastic bands, which arise on the scapular tuberosity and end on the lips of the bicipital groove. A pad of fat is interposed between the capsule and the tendon of the biceps. Ligaments are absent from this joint, but the muscles and tendons around it afford remarkable security, so that dislocation seldom or never occurs. The large extent of the head of the humerus is also of importance in this regard. The principal muscles which are attached around the joint and act as ligaments are: externally, the supraspinatus, infraspinatus, and teres minor; internally, the subscapularis; in front, the biceps and supraspinatus; behind, the triceps.