The Pedestrian's Record

2 1 2 THE PEDESTRIAN'S RECORD. wards. The latissimus dorsi, when the shoulder and arm are rendered fixed,assists powerfully during laboured breathing by drawing on and elevating the lower ribs ; by combining with the abominal andpectoral musclesit sustains the body in the effort of climbing, and in association with the pectoralis major becomes the most potent agentin effecting thelocomotion of a man on crutches. The trapeziusand latissimus dorsi actalso upon the spine, i.e., when the shoulder and arm become fixed points a man running on a cinder-track in turning corners inclines his body, and itwould incline too far, and his equilibrium would be lost, were notthe arm on the opposite side thrown out from the trunk, so as to render the insertion of the latissimus dorsi on the humerus a fixed point, when its fibres, acting onthe spine, keep thevertebrae ina right line. THE OUTSIDE OF THE ARM. The deltoid is situated on the upper and outer part of the arm. It arises from the scapula andclavicle, andis inserted into the humerus, and covers the entire shoulder-joint. The bicepslies on the forepart of the arm, extendingfrom the scapula to the forearm. This muscleis overlapped above by the deltoid andpectoral muscles. Brachialis is covered by the biceps along the lower half ot the arm. It arises fromthe humerus. At the insertion of the deltoid it passes in front of the elbow, and is inserted on the forepart ofthe ulna. Triceps : situated on the back part of the humerus, and ex­ tends fromthe scapula to the ulna. Action of the biceps is that of flexing the elbow ;and when the arm is held in fixed position, suchas is noticed in drawing the chin on thecrossbar, then the biceps and brachialis draw on the humerus and flex the arm, producing that exhibition of mus­ cular developmentof which young athletes are so proud. The triceps is the antagonist of the biceps and brachialis, and