36? 



FOIIE-ARM. 



vein ; its brandies are numerous throughout 

 its course, which terminates at the wrist-joint 

 in the supply of branches to the skin on the 

 dorsumand ball of the thumb, which inosculate 

 with the cutaneous of the radial. 



This last-mentioned branch, the cutaneous of 

 the rudiul, is derived from its trunk on the 

 outer side of the middle of the arm ; imme- 

 diately after that nerve has emerged from 

 between the triceps extensor and the bone, a 

 series of branches is distributed to the skin 

 of the arm. The remainder of the nerve, 

 which is a descending branch of some size, 

 passes down behind the elbow-joint, and be- 

 coming subcutaneous supplies the skin of the 

 posterior surface of the outer half of the fore- 

 arm, and corresponds to the musculo-cutaneous 

 on the anterior. Thus it will be seen that 

 the skin on the inner side of the fore-arm, 

 both anteriorly and posteriorly, is supplied by 

 the internal cutaneous, while that on the outer 

 side is supplied in front by the musculo-cu- 

 taneous, and behind by the radial nerve. 



The superficial veins of the fore-arm, though 

 subject to the greatest variety, are usually 

 distinguished by the names of the cephalic, 

 basilic, and median. The two first commence 

 on the back of the hand ; the cephalic on the 

 external, and the basilic on the internal side. 

 They freely anastomose at the lower part of 

 the fore-arm, after which they separate, and 

 reaching the anterior surface below the elbow, 

 are joined by the median vein, as described 

 in the article ELBOW. 



The superficial absorbents take nearly the 

 same course as the veins, though they are 

 far more numerous, and on the whole pursue 

 a straighter direction. The course of these 

 vessels is occasionally demonstrated in the living 

 subject by active inflammation of their coats 

 following the absorption of irritating matter. 



Aponeurosis. The aponeurosis of the fore- 

 arm is simply a continuation of the same 

 structure, which surrounds and supports the 

 muscles of the upper arm ; it varies very much 

 in density and appearance in different situa- 

 tions ; this difference arises from the fact that 

 both the triceps extensor and biceps flexor 

 cubiti send to it many fibres, which not merely 

 give additional strength to its texture, but also 

 act as a medium through which these muscles 

 possess the power of making tense the fascia. 

 This provision for tightening and supporting 

 the fascia of the fore-arm is analogous to those 

 arrangements which we meet with in the thigh 

 and leg. 



The fascia of the fore-arm is strongest at the 

 posterior part of the limb, on each side of the 

 olecranon. The fibres derived from the tendon 

 of the triceps on the external side pass trans- 

 versely outwards to be inserted into the outer 

 condyle, intermingling witli the radial exten- 

 sors at their origin, at the same time firmly 

 connected to the olecranon process, posteriorand 

 internal edge of the ulna, thus forming a dense 

 and firm covering to the anconeus, between 

 which muscle and the extensor carpi ulnaris a 

 process of fascia is met with which forms a 



dense septum between the two. The fibres 

 from the internal edge of the triceps at the 

 upper part also pass transversely, reaching the 

 inner condyle, intermingle with the origin of 

 the flexor muscles ; others again, descending at 

 the back part of the arm, form an aponeurosis 

 over the flexor carpi ulnaris; while those which 

 pass forwards intermingle with the aponeurotic 

 fibres of the biceps. These fibies from the 

 biceps are uniformly strong and distinct, and 

 give a great firmness and density to the f.iscia 

 on the inner side of the arm covering the flexor 

 muscles, which is not met with on the outer 

 side of the arm supporting the supinators. 

 The fascia in front of the fore-arm which covers 

 the supinators receives its last fibrous connexion 

 from the tendon of the deltoid. The fascia of 

 the fore-arm on reaching the posterior part of 

 the wrist-joint has interwoven with its texture 

 many beautifully distinct fibres, taking a 

 slightly oblique course from without to within, 

 and from above to below ; these fibres, which 

 are firmly attached to the radius on the outer 

 side and the ulna on the inner, become insen- 

 sibly lost in the fascia on the back part of the 

 hand, which resembles in its homogeneous 

 appearance the fascia on the lower part of the 

 fore-arm ; these supplementary fibres to the 

 fascia, though presenting a distinct edge neither 

 above nor below, act as a ligament to the exten- 

 sor tendons in their passage behind the wrist- 

 joint, which has been called by some anatomists 

 the posterior annular ligament ; between these 

 tendons and the ligament there is a large and 

 distinct bursa, not unfrequently the seat of 

 inflammation. The fascia on the lower and 

 fore part of the fore-arm, consisting principally 

 of transverse fibres, becomes gradually thinner, 

 and in front of the wrist-joint is inseparably in- 

 terwoven with the fibres of the annular ligament. 

 The aponeurosis of the fore-arm forms many 

 septa between the muscles. Commencing with 

 the description of the septa in the back part of 

 the arm, we find a dense and strong one sepa- 

 rating the anconeus from the extensor carpi 

 ulnaris, and from which the latter muscle takes 

 part of its origin. A second dips between the 

 extensor carpi ulnaris and extensor communis 

 digitorum, giving origin to both. A third is 

 found between the common extensors of the fin- 

 gers and radial extensors. The radial extensors 

 and supinators are not thus separated from each 

 other. A fourth process, distinct though com- 

 paratively thin, separates the snpinator radii 

 longus from the brachialis anticus, the tendon 

 of the biceps, pronator radii teres, and flexor 

 carpi radialis. There is also another process 

 which unites the tendon of the supinator radii 

 longus on the outer side to the flexor carpi 

 ulnaris on the inner side, and forms a firm and 

 dense covering to the radial artery. The pro- 

 nator radii teres is scarcely separated from the 

 flexor carpi radialis by a distinct septum, 

 though the last-mentioned muscle is completely 

 separated from the palmaris longus by a dipping 

 in of the fascia. Between the flexor communis 

 digitorum sublimis and flexor carpi ulnaris 

 there is a very perfect and distinct septum. 



