1326 SURFACE ANATOMY AND SURFACE MARKINGS 



binds the skin so firmly to the palmar aponeurosis that very little movement is 

 permitted between the two. 



On the back of the hand and fingers the subcutaneous tissue is lax, so that the 

 skin is freely movable on the underlying parts. Over the interphalangeal joints 

 the skin is very loose and is throw r n into transverse wrinkles when the fingers 

 are extended. 



Bones. The clavicle can be felt throughout its entire length. The enlarged 

 sternal extremity projects above the upper margin of the sternum at the side of 

 the jugular notch, and from this the body of the bone can be traced lateralward 

 immediately under the skin. The medial part is convex forward, but the surface 

 is partially obscured by the attachments of Sternocleidomastoideus and Pectoralis 

 major; the lateral third is concave forward and ends at the acromion of the scapula 

 in a slight enlargement. The clavicle is almost horizontal when the arm is lying 

 by the side, although in muscular subjects it may incline a little upward at its 

 acromial end, which is on a plane posterior to the sternal end. 



The only parts of the scapula that are truly subcutaneous are the spine and 

 acromion, but the coracoid process, the vertebral border, the inferior angle, and to 

 a lesser extent the axillary border can also be readily defined. The acromion and 

 spine are easily recognizable throughout their entire extent, forming with the 

 clavicle the arch of the shoulder. The acromion forms the point of the shoulder; 

 it joins the clavicle at an acute angle the acromial angle slightly medial to, and 

 behind the tip of the acromion. The spine can be felt as a distinct ridge, marked 

 on the surface as an oblique depression which becomes less distinct and ends in a 

 slight dimple a little lateral to the spinous processes of the vertebra?. Below this 

 point the vertebral border can be traced downward and lateralward to the inferior 

 angle, which can be identified although covered by Latissimus dorsi. From the 

 inferior angle the axillary border can usually be traced upward through its thick 

 muscular covering, forming with its enveloping muscles the posterior fold of the 

 axilla. The coracoid process is situated about 2 cm. below the junction of the 

 intermediate and lateral thirds of the clavicle; it is covered by the anterior border 

 of Deltoideus, and thus lies a little lateral to the infraclavicular fossa or depression 

 which marks the interval between the Pectoralis major and Deltoideus. 



The humerus is almost entirely surrounded by muscles, and the only parts 

 which are strictly subcutaneous are small portions of the medial and lateral epi- 

 condyles; in addition to these, however, the tubercles and a part of the head of the 

 bone can be felt under the skin and muscles by which they are, covered. Of these, 

 the greater tubercle forms the most prominent bony point of the shoulder, extending 

 beyond the acromion; it is best recognized when the arm is lying passive by the 

 side, for if the arm be raised it recedes under the arch of the shoulder. The lesser 

 tubercle, directed forward, is medial to the greater and separated from it by the 

 intertubercular groove, which can be made out by deep pressure. When the arm 

 is abducted the lower part of the head of the humerus can be examined by pressing 

 deeply in the axilla. On either side of the elbow-joint and just above it are the 

 medial and lateral epicondyles. Of these, the former is the more prominent, but the 

 medial supracondylar ridge passing upward from it is much less marked than the 

 lateral, and as a rule is not palpable; occasionally, however, the hook-shaped supra- 

 condylar process (page 211) is found on this border. The position of the lateral 

 epicondyle is best seen during semiflexion of the forearm, and is indicated by 

 a depression; from it the strongly marked lateral supracondylar ridge runs 

 upward. 



The most prominent part of the ulna, the olecranon, can always be identified at 

 the back of the elbow-joint. When the forearm is flexed the upper quadrilateral 

 surface is palpable, but during extension it recedes into the olecranon fossa. During 

 extension the upper border of the olecranon is slightly above the level of the medial 





