inserted into the ramus of the lower jaw. Their action is to close the mouth and assist in mastication. The Occipito-frontalis, the Orbicularis palpebrarum, and Orbicularis oris muscles are largely concerned in wrinkling the forehead, closing the eyes and mouth, and in giving various expressions to the face.

The Deltoid is a thick, triangular muscle covering the shoulder joint. Arising from the outer third of the clavicle, the acromion process and the spine of the scapula, its fibers converge to be inserted into the humerus just above its middle. Its action is to elevate the arm through a right angle. Owing to its point of insertion it acts as a lever of the third order, but, notwithstanding the advantageous point of insertion, it acts at a considerable disadvantage, owing to the obliquity of its direction. The Biceps muscle, situated on the anterior aspect of the the upper border of the glenoid fossa and the coraccid process, and is inserted into the radius just beyond the elbow joint. Its action is to flex and supinate the forearm and to place it in the most favorable position for striking a blow. When the forearm is fixed it assists in flexing the arm, as in climbing.

arm,

arises from

The Triceps muscle, situated on the back of the arm, arises from the scapula and the posterior surface of the humerus, and is inserted in the olecranon process of the ulna. In its action it directly antagonizes the biceps, namely, extending the forearm. In so doing it acts as a lever of the first order. The short distance between the muscular insertion and the fulcrum causes it to act at a great mechanical disadvantage, but there is a corresponding gain in both speed and range of movement. The muscles of the forearm are very numerous. Their action is to impart to the forearm and hand a variety of movements, such as pronation, supination, flexion, extension, rotation, etc.

The Pectoralis Major and Minor muscles form the fleshy masses of the breast. Arising from the inner half of the clavicle, the side of the sternum, and the outer surfaces of the third, fourth, and fifth ribs anteriorly, the muscular fibers converge to be inserted into the humerus and coracoid process. Their combined action is to adduct, flex, and rotate the arm inward, and to draw the scapula downward and forward, movements necessary to the folding of the arms across the chest.

The Rectus abdominis and the Obliquus externus assist in forming the abdominal walls.

The Glutei muscles are three in number, arranged in layers, and form the fleshy masses known as the buttocks. They arise from the side of the pelvis and are attached to the femur in the neighborhood of the great tro