OCR Text |
Show 814 MR. G. E. DOBSON ON THE ANATOMY [June 21, with that of the pectoralis major; some of the fibres of its scapular portion are inserted into the superficial fascia of the arm. Bhom-boideus consists of two parts of nearly equal extent: the first arises from the occipital bone under cover of part of the cleido-occipital and the trapezius, the second from the ligamentum nuchse (as far forwards as the second dorsal spine) and from two or three dorsal spines, and is inserted into the inner side of the posterior margin of the scapula external to the insertion of the occipital part. Latissimus dorsi divides near the axilla into two parts ; the smaller is united to and inserted with the teres major ; the other part, many times larger, after giving off the dorso-epitrochlearis, suddenly narrows into a small tendon which is inserted into the bicipital groove. The dorsa-epitrochlearis is enormous, covering the greater part of the posterior and inner side of the arm ; it is inserted by a tendinous expansion. The coraco-Brachialis is closely united with the short head of the Biceps; it is inserted into the humerus above the middle; but a fasciculus of muscular fibres continuous with it passes on with the Biceps, and is inserted with the latter into the radius. Covered by this muscle at its origin, a short but broad muscle, the coraco-Brachialis Brevis (rotator humeri, W o o d ) arises, and is inserted into the neck of the humerus below the lesser tuberosity. The extensor ossis metacarpi pollicis is very large, and has but a single tendon, inserted into the proximal extremity of the first metacarpal bone. Extensor secundi internodii pollicis is feeble, and has a single long tendon. Extensor communis digitorum sends three tendons to the three middle digits. Extensor minimi digiti forms two long tendons in the arm, which are inserted into the outer and inner sides of the fifth digit. Extensor indicts has also two tendons ; one goes to the second digit, the other to the third, gives off also a tendon to the fourth digit. There is no trace of an extensor primi internodii pollicis. Palmaris longus, arising with the flexor carpi radialis, is inserted as usual into the palmar fascia, from which a muscular bundle of fibres arises on the radial side, and is inserted into the integument of the palm ; the corresponding integumentary muscle on the ulnar side is the palmaris Brevis, which arises wholly from the pisiform bone and annular ligament. Flexor digitorum profundus arises by three heads, which, however, are closely connected together, the only approximately distinct one being that arising from the outer side of the ulna, which gives origin to the tendon for the fifth digit. The tendon for the pollex arises from the superficial surface of the c o m m o n tendon; it is very much smaller than the other tendons. From the annular ligament near the insertion of the tendon of the flexor carpi radialis arises a small muscle, the fibres of which occupy a space scarcely exceeding that which would be taken by a split pea ; this muscle forms a very slender tendon, which, passing superficially across the large aBductor pollicis, gets to the ulnar |