1328 SURFACE ANATOMY AND SURFACE MARKINGS 





first and second phalanges are slightly hollow, but flattened and square-shaped in 

 those between the second and third. 



Articulations. The sternoclavicular joint is subcutaneous, and its position is 

 indicated by the enlarged sternal extremity of the clavicle, lateral to the long 

 cord-like sternal head of Sternocleidomastoideus. If this muscle .be relaxed a 

 depression between the end of the clavicle and the sternum can be felt, defining 

 the exact position of the joint. 



The position of the acromioclavicular joint can generally be ascertained by 

 determining the slightly enlarged acromial end of the clavicle which projects above 

 the level of the acromion; sometimes this enlargement is so considerable as to 

 form a rounded eminence. 



The shoulder- joint is deeply seated and cannot be palpated. If the forearm 

 be slightly flexed a curved crease or fold with its convexity downward is seen in 

 front of the elbow, extending from one epicondyle to the other; the elbow-joint 

 is slightly distal to the center of the fold. The position of the radiohumeral joint 

 can be ascertained by feeling for a slight groove or depression between the head 

 of the radius and the capitulum of the humerus, at the back of the elbow-joint. 



The position of the proximal radioulnar joint is marked on the surface at the 

 back of the elbow by the dimple which indicates the position of the head of the 

 radius. The site of the distal radioulnar joint can be defined by feeling for the 

 slight groove at the back of the wrist between the prominent head of the ulna 

 and the lower end of the radius, when the forearm is in a state of almost complete 

 pronation. 



Of the three transverse skin furrows on the front of the wrist, the middle corre- 

 sponds fairly accurately with the wrist-joint, while the most distal indicates the 

 position of the midcarpal articulation. 



The metacarpophalangeal and interphalangeal joints are readily available for 

 surface examination; the former are situated just distal to the prominences of the 

 knuckles, the latter are sufficiently indicated by the furrows on the volar, and the 

 wrinkles on the dorsal surfaces. 



Muscles (Figs. 1194, 1231, 1232). The anterior border of the Trapezius presents as 

 a slight ridge running downward and forward from the superior nuchal line of the 

 occipital bone to the junction of the intermediate and lateral thirds of the clavicle. 

 The inferior border of the muscle forms an undulating ridge passing downward 

 and medialward from the root of the spine of the scapula to the spinous process 

 of the twelfth thoracic vertebra. 



The lateral border of the Latissimus dorsi (Fig. 1215) may be traced, when the 

 muscle is in action, as a rounded edge starting from the iliac crest and slanting 

 obliquely forward and upward to the axilla, where it takes part with the Teres 

 major in forming the posterior axillary fold. 



The Pectoralis major (Fig. 1219) conceals a considerable part of the thoracic wall 

 in front. Its sternal origin presents a border which bounds, and determines the 

 width of the sternal furrow. The upper margin is generally well-marked medially 

 and forms the medial boundary of a triangular depression, the infraclavicular fossa, 

 which separates the Pectoralis major from the Deltoideus; it gradually becomes 

 less marked as it approaches the tendon of insertion and is closely blended with 

 the Deltoideus. The lower border of Pectoralis major forms the rounded anterior 

 axillary fold. Occasionally a gap is visible between the clavicular and sternal parts 

 of the muscle. 



When the arm is raised the lowest slip of origin of Pectoralis minor produces a 

 fulness just below the anterior axillary fold and serves to break the sharp outline 

 of the lower border of Pectoralis major. 



The origin of the Serratus anterior (Figs. 1215, 1219) causes a very characteristic 

 surface marking. When the arm is abducted the lower five or six serrations form 



