Page:EB1911 - Volume 19.djvu/71

 points of practical interest about these muscles are noticed in the article (Superficial and Artistic). In addition to these the brachio-radialis is a flexor of the forearm, though it arises from the outer supracondylar ridge of the humerus. It is supplied by the musculo-spiral nerve, the flexor carpi ulnaris by the ulinar, the rest by the median. The deep muscles of the front of the forearm consist of the flexor longus pollicis running from the radius to the terminal phalanx of the thumb, the flexor profundus digitorum from the ulna to the terminal phalanges of the fingers, and the pronator quadratus passing across from the lower third of the ulna to the same amount of the radius. These three muscles are supplied by the anterior interosseous branch of the median nerve, but the flexor profundus digitorum has an extra twig from the ulnar. The extensor muscles at the back of the forearm are also divided into superficial and deep sets (see fig. 8). The former rise from the region of the external condyle of the humerus, and consist of the extensor carpi radialis longior and brevior inserted into the index and medius metacarpal bones, the extensor communis digitorum to the middle and distal phalanges of the fingers, the extensor minimi digiti, the extensor carpi ulnaris passing to the metatarsal bone of the minimus, and the supinator brevis wrapping round the neck of the radius to which it is inserted. The aconeus which runs from the external condyle to the olecranon process is really a part of the triceps. The deep muscles rise from the posterior surfaces of the radius and ulna, and are the extensor ossis metacarpi pollicis, the name of which gives its insertion, the extensor brevis pollicis to the proximal phalanx, and the extensor longus pollicis to the distal phalanx of the thumb, while the extensor indicis joins the extensor communis slip to the index finger; all these posterior muscles are supplied by the posterior interosseous nerve. In front and behind the wrist the tendons are bound down by the anterior and posterior annular ligaments, while on the flexor surface of each finger is a strong fibrous sheath or theca for the flexor tendons. The ball of the thumb is occupied by short muscles called the thenar group, while hypothenar muscles are found in the ball of the little finger. The four lumbrical muscles (fig. 9, d) run from the flexor profundus digitorum tendons to those of the