498 THE MUSCLES AND FASCIA. 



Pectoralis major. Its posterior border is thin, flattened, and scarcely marked above ; below, it 

 is thicker and more prominent. When the muscle is in action, the middle portion becomes 

 irregular, presenting alternate longitudinal elevations and depressions, the elevations correspond- 

 ing to the flesh\ ? portions, the depressions to the tendinous intersections of the muscle. The 

 insertion of the Deltoid is marked by a depression on the outer side of the middle of the arm. 

 Of the scapular muscles, the only one which materially influences surface form is the Teres 

 major, which assists the Latissimus dorsi in forming the thick, rounded fold of the posterior 

 boundary of the axilla. When the arm is raised, the Coraco-brachialis reveals itself as a long, 

 narrow elevation which emerges from under cover of the anterior fold of the axilla and runs 

 downward, internal to the shaft of the hunierus. When the arm is hanging by the side, its 

 front and inner part presents the prominence of the Biceps, bounded on either side by an inter- 

 muscular depression. This muscle determines the contour of the front of the arm, and extends 

 from the anterior margin of the axilla to the bend of the elbow. Its upper tendons are con- 

 cealed by the Pectoralis major and the Deltoid, and its lower tendon sinks into the space at the 

 bend of the elbow. When the muscle is in a state of complete contraction that is to say, 

 when the forearm has been flexed and supinated it presents a rounded convex form, bulged 

 out laterally, and its length is diminished. On each side of the Biceps, at the lower part of 

 the arm, the BracMalis anticus is discernible. On the outer side it forms a narrow eminence 

 which extends some distance up the arm along the border of the Biceps. On the inner side it 

 shows itself only as a little fulness just above the elbow. On the back of the arm the long head 

 of the Triceps may be seen as a longitudinal eminence emerging from under cover of the Deltoid, 

 and gradually merging into the longitudinal flattened plane of the muscle on the lower part of 

 the back of the arm. On the anterior aspect of the elbow are to be seen two muscular eleva- 

 tions, one on each side, separated above and converging below so as to form a triangular space. 

 Of these, the inner elevation, consisting of the flexors and pronator, forms the prominence 

 along the inner side and front of the forearm. It is a fusiform mass, pointed above at the 

 internal condyle and gradually tapering off below. The Pronator radii tercs, the innermost 

 muscle of the group, forms the boundary of the triangular space at the bend of the elbow. It 

 is shorter, less prominent, and more oblique than the outer boundary. The most prominent 

 part of the eminence is produced by the Flexor carpi radialis, the muscle next in order on the 

 inner side of the preceding one. It forms a rounded prominence above, and can be traced 

 downward to its tendon, which can be felt lying on the front of the wrist, nearer to the radial 

 than to the ulnar border, and to the inner side of the radial artery. The Palmaris longus 

 presents no surface marking above, but below is the most prominent tendon on the front of the 

 wrist, standing out, when the muscle is in action, as a sharp, tense cord beneath the skin. The 

 Flexor sublimis digitorum does not directly influence surface form. The position of its four 

 tendons on the front of the lower part of the forearm is indicated by an elongated depression 

 between the tendons of the Palmaris longus and the Flexor carpi ulnaris. The Flexor carpi 

 ulnaris occupies a small part of the posterior surface of the forearm, and is separated from the 

 extensor and supinator group, which occupies the greater part of this surface, by the ulnar 

 furrow, produced by the subcutaneous posterior border of the ulna. Its tendon can be perceived 

 along the ulnar border of the front of the forearm, and is most marked when the hand is flexed 

 and adducted. The deep muscles of the front of the forearm have no direct influence on surface 

 form. The external group of muscles of the forearm, consisting of the extensors and supi- 

 nators, occupy the outer and a considerable portion of the posterior surface of this region. They 

 form a fusiform mass, which is altogether on a higher level than the pronato-flexor group. Its 

 apex emerges from between the Triceps and Brachialis anticus muscles some distance above the 

 elbow-joint, and acquires its greatest breadth opposite the external condyle, and thence gradually 

 shades off into a flattened surface. About the middle of the forearm it divides into two longi- 

 tudinal eminences which diverge from each other, leaving a triangular interval between them. 

 The outer of these two groups of muscles consists of the Supinator longus and the Extensor 

 carpi radialis longior et brevior, which form a longitudinal eminence descending from the exter- 

 nal condyloid ridge in the direction of the styloid process of the radius. The other and more 

 posterior group consists of the Extensor communis digitorum. the Extensor minimi digit! . and 

 the Extensor carpi ulnaris. It commences above as a tapering form at the external condyle of 

 the humerus, and is separated behind at its upper part from the Anconeus by a well-marked 

 furrow, and below, from the pronato-flexor mass, by the ulnar furrow. In the triangular inter- 

 val left between these two groups the extensors of the thumb and index finger are seen. The 

 only two muscles of this region which require special mention as independently influencing 

 surface form are the Supinator longus and the Anconeus. The inner border of the Supinator 

 longus forms the outer boundary of the triangular space at the bend of the elbow. It com- 

 mences as a rounded border above the condyle, and is longer, less oblique, and more prominent 

 than the inner boundary. Lower down, the muscle forms a full fleshy mass on the outer side of 

 the upper part of the forearm, and below tapers into a tendon, which may be traced down to 

 the styloid process of the radius. The Anconeus presents a well-marked and characteristic 

 surface form in the shape of a triangular, slightly elevated surface, immediately external to the 

 subcutaneous posterior surface of the olecranon, and differentiated from the common extensor 

 group by a well-marked oblique longitudinal depression. The upper angle of the triangle corre- 

 sponds to the external condyle, and is marked by a depression or dimple in this situation. In 

 the triangular interval caused by the divergence from each other of the two groups of muscles 

 into which the extensor and supinator group is divided at the lower part of the forearm an 



