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Henry Gray (1825–1861).  Anatomy of the Human Body.  1918.
 
the radius to the radial side of the wrist-joint, whence it is continued on to the dorsal surface of the thumb as a ridge best marked when the thumb is extended.
  The tendons of most of the Extensor muscles can be seen and felt on the back of the wrist. Laterally is the oblique ridge produced by the Extensor pollicis longus. The Extensor carpi radialis longus is scarcely palpable, but the Extensor carpi radialis brevis can be identified as a vertical ridge emerging from under the ulnar border of the tendon of the Extensor pollicis longus when the wrist is extended. Medial to this the Extensor tendons of the fingers can be felt, the Extensor digiti quinti proprius being separated from the tendons of the Extensor digitorum communis by a slight furrow.
  The muscles of the hand are principally concerned, as regards surface form, in producing the thenar and hypothenar eminences, and cannot be individually distinguished; the thenar eminence, on the radial side, is larger and rounder than the hypothenar, which is a long narrow elevation along the ulnar side of the palm. When the Palmaris brevis is in action it produces a wrinkling of the skin over the hypothenar eminence and a dimple on the ulnar border. On the back of the hand the Interossei dorsales give rise to elongated swellings between the metacarpal bones; the first forms a prominent fusiform bulging when the thumb is adducted, the others are not so marked.

Arteries.—Above the middle of the clavicle the pulsation of the subclavian artery can be detected by pressing downward, backward, and medialward against the first rib. The pulsation of the axillary artery as it crosses the second rib can be felt below the middle of the clavicle just medial to the coracoid process; along the lateral wall of the axilla the course of the artery can be easily followed close to the medial border of Coracobrachialis. The brachial artery can be recognized in practically the whole of its extent, along the medial margin of the Biceps; in the upper two-thirds of the arm it lies medial to the humerus, but in the lower third is more directly on the front of the bone. Over the lower end of the radius, between the styloid process and Flexor carpi radialis, a portion of the radial artery is superficial and is used clinically for observations on the pulse.

Veins.—The superficial veins of the upper extremity are easily rendered visible by compressing the proximal trunks; their arrangement is described on pages 660 to 662.

Nerves.—The uppermost trunks of the brachial plexus are palpable for a short distance above the clavicle as they emerge from under the lateral border of Sternocleidomastoideus; the larger nerves derived from the plexus can be rolled under the finger against the lateral axillary wall but cannot be identified. The ulnar nerve can be detected in the groove behind the medial epicondyle of the humerus.
 
12. Surface Markings of the Upper Extremity
 

Bony Landmarks.—The bony landmarks as described above are so readily available for surface recognition that no special measurements are required to indicate them. It may be noted, however, that the medial angle of the scapula is applied to the second rib, while the inferior angle lies against the seventh. The intertubercular groove of the humerus is vertically below the acromioclavicular joint when the arm hangs by the side with the palm of the hand forward.

Articulations.—The acromioclavicular joint is situated in a plane passing sagittally through the middle line of the front of the arm. The line of the elbow-joint is not straight; the radiohumeral portion is practically at right angles to the long axis of the humerus and is situated about 2 cm. distal to the lateral epicondyle; the ulnohumeral portion is oblique, and its medial end is about 2.5 cm. distal to the medial epicondyle. The position of the wrist-joint can be indicated by drawing a

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