410 THE MUSCLES AND FASCIA. 



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 anticns 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 tendon of the muscle on the 

 lower part of the back of the arm. The tendon of insertion of the muscle extends about half- 

 way up the back of the arm, where it forms an elongated flattened plane when the muscle is in 

 action. Under similar conditions the surface forms produced by the three heads of the muscle 

 are well seen. On the anterior aspect of the elbow are to be seen two muscular elevations, 

 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 mill I. feres, 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 radiah's, 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 suUimis digitorwn 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. It 

 has a fusiform outline, 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 grad- 

 ually shades off" into a flattened surface. About the middle of the forearm it divides into two 

 longitudinal 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 condylar 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 digiti, 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 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 oblique 

 elongated eminence is seen, caused by the emergence of two of the extensors of the thumb 

 from their deep origin at the back of the forearm. This eminence, full above and becoming 

 flattened out and partially subdivided below, runs downward and outward over the back 

 and outer surface of the radius to the outer side of the wrist-joint, where it forms a ridge, 

 especially marked when the thumb is extended, which passes onward to the posterior aspect of 

 the thumb. The tendons of most of the extensor muscles are to be seen and felt at the level 

 of the wrist-joint. Most externally are the tendons of the Extensor ossis metacarpi polhcis and 



