In its upper part the _brachial artery_ lies internal to the humerus but below it is in front of the bone. The _radial_ runs in a line from the middle of the elbow anteriorly to the inner side of the styloid process of the radius and is much exposed to injury in the lower third of its course, as when the hand is thrust through glass. On it at the wrist the pulse is counted. It is much smaller than the ulnar and winds around the outer side of the thumb to the palm, where, with the deep branch from the ulnar, it forms the _deep palmar arch_. The _ulnar artery_ passes obliquely inward to the middle of the forearm and thence along its ulnar border to the palm of the hand, where it divides into the deep branch and the _superficial palmar arch_ which supplies the four _digital arteries_. From the _axillary artery_ branches go to the chest wall and shoulder, the most important being the two _circumflex arteries_ to the deltoid. The brachial has only two branches of any importance, the _superior_ and _inferior profunda_, both on the upper arm, of course. In case of _hemorrhage_ compression can frequently be applied with the fingers where the subclavian crosses the rib or in the axilla, where the artery can be pressed up against the humerus. =Nerves.=--The nerve supply of the shoulder comes chiefly from the anterior and posterior _thoracic_, the _suprascapular_, and the _circumflex_, these last going to the deltoid. The biceps is supplied by the _musculo-cutaneous_, the triceps by the _musculo-spiral_, and the brachialis anticus by both. Most of the flexor and pronator muscles are supplied by the _median_, while the _posterior interosseous_ and the _musculo-spiral nerves_ go to the extensors and supinators. The _ulnar nerve_ supplies the hand largely. CHAPTER XIII. THE LOWER EXTREMITIES. The lower extremities resemble the upper very closely in the arrangement of the bones, muscles, arteries, and nerves, though modifications occur, due to the difference in function of the lower limbs. There is one long bone in the upper part or thigh, the femur, and two in the lower part or leg, the tibia and fibula, while over the knee-joint is the patella or knee-cap. The ankle has seven bones and the foot nineteen like the hand. =The Femur.=--The femur is the longest bone in the body, being about one-fourth the height of the person. It inclines toward its fellow at the knee in order to bring the knee-joints near the center of gravity in walking, the amount of inclination varying with the width of the hips and the height of the person. On account of the greater width of hip the tendency to knock-knee is greater in women than in men.