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Henry Gray (1825–1861).  Anatomy of the Human Body.  1918.
 
arm, but at the middle of the arm it diverges and descends to the back of the medial epicondyle. In the forearm it is represented by a line from the front of the medial epicondyle to the radial side of the pisiform bone.
  The course of the radial nerve can be indicated by a line from just below the posterior axillary fold, to the lateral side of the humerus at the junction of its middle and lower thirds; thence it passes vertically downward on the front of the arm to the level of the lateral epicondyle. The course of the superficial radial nerve is represented by a continuation of this line downward to the junction of the middle and lower thirds of the radial artery; it then crosses the radius and runs distalward to the dorsum of the base of the first metacarpal bone.
  The axillary nerve crosses the humerus about 2 cm. above the center of a line joining the tip of the acromion to the lower edge of the deltoid tuberosity.
 
13. Surface Anatomy of the Lower Extremity
 

Skin.—The skin of the thigh, especially in the hollow of the groin and on the medial side, is thin, smooth and elastic, and contains few hairs except on the neighborhood of the pubis. Laterally it is thicker and the hairs are more numerous. The junction of the skin of the thigh with that on the front of the abdomen is marked by a well-defined furrow which indicates the site of the inguinal ligament; the furrow presents a general convexity downward, but its medial half, which is the better marked, is nearly straight. The skin over the buttock is fairly thick and is characterized by its low sensibility and slight vascularity; as a rule it is destitute of conspicuous hairs except toward the post-anal furrow, where in some males they are abundantly developed. An almost transverse fold—the gluteal fold—crosses the lower part of the buttock; it practically bisects the lower margin of the Glutæus maximus and is most evident during extension of the hip-joint. The skin over the front of the knee is covered by thickened epidermis; it is loose and thrown into transverse wrinkles when the leg is extended. The skin of the leg is thin, especially on the medial side, and is covered with numerous large hairs. On the dorsum of the foot the skin is thin, loosely connected to subjacent parts, and contains few hairs, on the plantar surface, and especially over the heel, the epidermis is of great thickness, and here, as in the palm of the hand, there are neither hairs nor sebaceous glands.

Bones.—The hip bones are largely covered with muscles, so that only at a few points do they approach the surface. In front the anterior superior iliac spine is easily recognized, and in thin subjects stands out as a prominence at the lateral end of the fold of the groin; in fat subjects its position is indicated by an oblique depression, at the bottom of which the bony process can be felt. Proceeding upward and backward from this process the sinuously curved iliac crest can be traced to the posterior superior iliac spine, the site of which is indicated by a slight depression; on the outer lip of the crest, about 5 cm. behind the anterior superior spine, is the prominent iliac tubercle. In thin subjects the pubic tubercle is very apparent, but in the obese it is obscured by the pubic fat; it can, however, be detected by following up the tendon of origin of Adductor longus. Another part of the bony pelvis which is accessible to touch is the ischial tuberosity, situated beneath the Glutæus maximus, and, when the hip is flexed, easily felt, as it is then uncovered by muscle.
  The femur is enveloped by muscles, so that in fairly muscular subjects the only accessible parts are the lateral surface of the greater trochanter and the lower expanded end of the bone. The site of the greater trochanter is generally indicated by a depression, owing to the thickness of the Glutæi medius and minimus which project above it; when, however, the thigh is flexed, and especially if it be crossed over the opposite one, the trochanter produces a blunt eminence on the surface.

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