EXTENSOR

LONGUS POLLICIS EXTENSOR  INDICIS From A . M . Paterson, Cunningham's Tat Book of Anatomy . 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 From A . M . Paterson, Cunningham's Text Book of Anatomy . 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 big toe, and the peroneus tertius, a purely human muscle inserted into the base of the fifth metatarsal bone . All these are supplied by the anterior tibial nerve . The external group comprises the peroneus longus and brevis, rising from the outer surface of the fibula and inserted into the tarsus (fig . I I), the longus tendon passing across the sole to the base of the first metatarsal bone, the brevis to the base of the fifth metatarsal . These are supplied by the musculo-cutaneous nerve . extensor communis between the heads of the metacarpal bones, while. rising from the shafts of these bones, are the three palmar and four dorsal interosseous muscles (fig . 9, e) which also are inserted into the extensor tendons . The two outer lumbricals and the thenar muscles are supplied by the median nerve; all the other hand muscles by the ulnar .