Posterior view of the ligaments of the elbow-joint. 1. Lower end of the humerus; 2. internal condyle; 3. external condyle; 4. the olecranon process of the ulna; 5. the upper portion of the radius; 6. the internal lateral ligament; 7. the external lateral ligament; 8. the posterior ligament.] [Illustration: Fig. LXXVI. View of the ligaments connecting the ulna and radius at their upper part. 1. The radius; 2. the ulna; 3. the coronary ligament surrounding the head of the radius; 4. the oblique ligament passing from the ulna to the tubercle of the radius; 5 the upper portion of the interosseous ligament.] 161. At their inferior extremities the ulna and radius are united partly by the interosseous ligament (fig. LXXVII. 1) and partly by ligamentous fibres which pass transversely from one bone to the other (fig. LXXVII. 2) on the anterior and the posterior surface of the fore-arm. [Illustration: Fig. LXXVII. 1. Interosseous ligament; 2. transverse fibres passing between the radius and ulna, and uniting the two bones; 3. 4. 5. posterior and lateral ligaments of the wrist joint; 6. ligaments uniting the bones of the wrist with one another; 7. 8. ligaments which attach the metacarpal to the carpal bones; 9. transverse ligaments for the attachment of the phalanges of the fingers; 10. lateral ligaments for the attachment of the phalanges of the fingers 11. ligaments of the thumb.] 162. The lower extremity of the radius is also united to the wrist; and the hand being attached to the wrist, the junction of the hand and the fore-arm is effected by the articulation of the wrist with the radius (fig. LXXVII.). The ligaments which connect the bones of the wrist with the radius are bands of exceeding strength (fig. LXXVII. 3). 163. The muscles that act upon the fore-arm are placed upon the arm (fig. LXXVIII.). The joint of the elbow being a hinge-joint, the fore-arm can admit only of two motions, namely, flexion and extension. The muscles by which these motions are effected are four, two for each; the two flexors being placed on the fore part (fig. LXXVIII. 2. 4), and the two extensors on the back part of the arm (fig. LXXIX. 5).