MUSCLES OF THE FORE-ARM. 



367 



one of the muscular septa previously referred to. 

 At the lower part of the upper third of the fore- 

 arm their separation is complete. The flexor 

 carpi radialis first changes its muscular fibres 

 for tendinous on its anterior face, and a rounded 

 tendon is the result at the upper part of the 

 lower third of the arm. This tendon passes in 

 front of the wrist-joint and through a groove in 

 the os trapezium, is ultimately inserted into the 

 base of the metacarpal bone supporting the 

 fore-finger. 



This muscle has on its outer edge, in the 

 superior third of the fore-arm, the pronator 

 radii teres, in the two inferior thirds the supi- 

 nator radii longus; the palmaris longus to its 

 inner edge, both at its origin and throughout 

 its whole course in the fore-arm. Anterior to 

 it there is simply the fascia, its posterior face 

 is in contact with the superficial flexor of the 

 fingers above and the long flexor of the thumb 

 below. The tendon of this muscle projects 

 distinctly through the skin at the lower part of 

 the arm. 



The flexor carpi radialis, besides flexing the 

 whole hand on the fore-arm, bends the second 

 row of carpal bones upon the first. It will also 

 act as an abductor of the hand, in consequence 

 of its being fixed on the outer side of the hand 

 in the pulley-like groove of the trapezium 

 through which it passes. It slightly assists the 

 pronator muscles in their influence over the hand. 



3. The palmaris longus, Soe'mm., epitrochlo- 

 palmaire, Chauss. The origin of this muscle, 

 which is in common with the other flexors, is 

 from the inner condyle, also from a tendinous 

 intermuscular septum which separates it from 

 the flexor carpi radialis on the outer side and 

 the flexor communis digitorum on the inner. 

 This muscle, the smallest of those situated in 

 the fore-arm, becomes tendinous midway be- 

 tween the elbow and wrist-joint. This tendon, 

 which is narrow and slender, descends to the 

 annular ligament, and is ultimately connected 

 with the palmar fascia. This fascia has some- 

 times been considered as a mere expansion of 

 the tendon of the palmaris longus, but as the 

 muscle is occasionally wanting and the fascia 

 never, we regard it rather as another instance 

 of that useful connexion of muscles with fascia? 

 which we have already had occasion to admire. 

 This muscle, except at its origin where it has 

 the flexor carpi radialis to its inner side and the 

 flexor communis to the outer, maintains a posi- 

 tion completely superficial to the other muscles, 

 its posterior face lying upon the flexor communis 

 sublimis. 



This muscle flexes the hand, and makes 

 tense the palmar fascia and annular ligament, 

 and thus takes off from the palmar vessels and 

 nerves and the tendons of the digital flexors the 

 pressure to which they are exposed when the 

 hand grasps a solid body firmly; as, for in- 

 stance, when the whole weight of the body is 

 sustained, as in the case of the sailor climbing 

 the rigging of a vessel, by the power of the 

 flexors of the fingers and hand. 



4. Flexor communis digitorum sublimis per- 

 foratus. ( Musculus perforatus, Soe'mm., epi- 



trochlo-phalanginien commun, Chauss.) This 

 muscle also arises from the inner condyle in 

 common with the other muscles, and from a 

 strong tendinous septum separating it from the 

 flexor carpi ulnaris. About the middle of the 

 fore-arm this portion of the muscle is joined by 

 muscular fibres which arise from the radius im- 

 mediately below the insertion of the supinator 

 radii brevis, and on the inner side of the pro- 

 nator radii teres. Between these two origins 

 of the flexor communis digitorum is placed the 

 median nerve. The tendinous fibres, into which 

 the muscle is gradually transformed, become 

 first apparent on the anterior surface, and next 

 being collected ultimately split into four cords, 

 which passing behind the annular ligament of 

 the wrist, enter the palm of the hand ; oppo- 

 site the first phalanx of the four fingers these 

 cords, splitting into two portions and allowing 

 the passage of the deep flexors, terminate by 

 being inserted in the rough edge on the sides 

 of the second phalanges. The tendons of this 

 muscle as well as the deep flexor are bound 

 down to the phalanges by smooth tendinous 

 sheaths or thecae which are dense and firm be- 

 tween the articulations, but insensibly disap- 

 pearing opposite the joint, where their presence 

 would interfere with the motion of the parts ; 

 they are lined by synovial membrane to prevent 

 unnecessary friction. 



Although the lateral width of this muscle is 

 considerable, only a very narrow edge is in 

 contact with the fascia, the remainder being 

 covered by the last-mentioned muscles, so that 

 some anatomists have described it as constitu- 

 ting a middle layer. 



On the internal edge is placed the flexor 

 carpi ulnaris, which maintains the same relative 

 position to it throughout the fore-arm. In 

 contact with its posterior face we have the 

 flexor digitorum profundus, the flexor longus 

 pollicis, and the ulnar artery, vein, and nerve. 



This muscle flexes the second phalanx on 

 the first, and the first on the metacarpus, and 

 the whole hand on the fore-arm. 



5. Flexor carpi ulnaris, (musculus ulnaris 

 internus, Soe'mm, cubital interne, Portal, cu- 

 bito-carpien, Chauss.) This muscle arises from 

 the internal extremity of the internal condyle 

 of the humerus from the tendinous intermuscu- 

 lar septum, between it and the flexor carpi digi- 

 torum sublimis, and from the olecranon process 

 of the ulna; between these two heads the ulnar 

 nerve is situated ; its origin from the ulna is 

 not limited to the olecranon process, for it con- 

 tinues its connexion with that bone nearly as 

 low down as the origin of the pronator quad- 

 ratus. This muscle, which arises tendinous 

 and fleshy, merges into tendinous fibres on its 

 anterior surface at the upper part of the lower 

 third of the fore-arm. The tendon by degrees 

 becomes more rounded, but does not cease to 

 receive fleshy fibres until it terminates by be- 

 coming inserted into the annular ligament and 

 os pisiforme. 



The flexor carpi ulnaris, forming the inner 

 margin of the muscles of the fore-arm, is in 

 contact with the fascia : its external edge touches 



