Page:EB1911 - Volume 19.djvu/70

 is attached to the deep surfaces of the ribs, and its fibres run horizontally forward. Below, all these muscles are attached to the crest of the ilium and to Poupart’s ligament, which is really the lower free edge of the external oblique, while, behind, the two deeper ones, at all events, blend with the fascia lumborum. As they approach the mid-ventral line they become aponeurotic and form the sheath of the rectus. The rectus abdominis (fig. 6) is a flat muscular band which runs up on each side of the linea alba or mid-ventral line of the abdomen from the pubis to the ribs and sternum. This muscle has certain tendinous intersections or lineae transversae, the positions of which are noticed in the article (Superficial and Artistic), and the morphology of which is referred to, later. In front of the lowest part of the rectus is sometimes a small triangular muscle called the pyramidalis. The quadratus lumborum is a muscle at the back of the abdominal wall which runs between the last rib and the crest of the ilium. In front of the bodies of the vertebrae is a prevertebral or hypaxial musculature, of which the rectus capitis anticus major and minor muscles and longus colli in the neck and the psoas in the loins form the chief parts, the latter being familiar as the undercut of the sirloin of beef. while the pelvis is closed below by a muscular floor formed by the levator ani and coccygeus muscles. The diaphragm is explained in a separate article. .—The deltoid (see figs. 7 and 8) is the muscle which forms the shoulder cap and is used in abducting the arm to a right angle with the trunk; it runs from the clavicle, acromial process and spine of the scapula, to the middle of the humerus, and is supplied by the circumflex nerve. Several short rotating muscles pass from the scapula to the upper end of the humerus; these are the subscapularis passing in front of the shoulder joint, the supraspinatus above the joint, and the infraspinatus and teres minor behind. The teres major (fig. 5) comes from near the lower angle of the scapula, and is inserted with the latissimus dorsi into the front of the, surgical neck of the humerus. The coracobrachialis (fig. 7) passes from the coracoid process to the middle of the humerus in front of the shoulder joint, while the brachialis anticus passes in front of the elbow from the humerus to the coronoid, process of the ulna. Passing in front of both shoulder and elbow is the biceps (fig. 7), the long head of which rises from the top of the glenoid cavity inside the joint, while the short head comes from the coracoid process, The insertion is into the tubercle of the radius. These three muscles are all supplied by the same (musculo-cutaneous) nerve. At the back of the arm is the triceps (fig. 8) which passes behind both shoulder and elbow joints and is the great extensor muscle of them; its long head rises from just below the glenoid cavity of the scapula, while the inner and outer heads come from the back of the humerus. It is inserted into the olecranon process of the ulna and is supplied by the musculo-spinal nerve. The muscles of the front of the forearm form superficial and deep sets (see fig. 7). Most of the superficial muscles come from the internal condyle of the humerus. From without inward they are the pronator radii teres going to the radius, the flexor carpi radialis to the base of the index metacarpal bone, the palmaris longus to the palmar fascia, the flexor sublimis digitorum to the middle phalanges of the fingers, and the flexor carpi ulnaris to the pisiform bone. The important