1336 SURFACE ANATOMY AND SURFACE MARKINGS 



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. 



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 neigh- 

 borhood 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 Glutseus 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 Glutseus 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 Glutsei 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. 





