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 with 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 fibres from the biceps are uniformly strong and distinct, and give a great firmness and density to the fascia 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 supinator 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.
Of the different morbid growths which arise in the cellular tissue of the fore-arm, those which are superficial and those which are beneath the fascia require careful distinction, the removal of the former being easily effected, while all operations on the latter require great consideration and care.
The superficial tumour projects under the skin, creating some deformity ; it may be moved with facility, for its attachments are loose ; while, on the other hand, the deep seated or sub-fascial tumour has frequently a flat tened surface, and often appears, on superficial examination, insignificant and of small extent, while in fact its mass is considerable, bur rowing deeply between the muscles. It is to be distinguished from the supra-faseial tumour by its comparative immobility, by the various effects produced upon it by the fascia when in a state of tension or relaxation, by the pain produced by pressure on nerves, or impediment to the circulation from pressure on the vessels. In the removal of the sub-fascial tumour the operator must call to mind the direction and relative position of the muscles in the neigh bourhood of it, as the roots or under surface of these generally follow the interspace between the muscles, and are thus guided to a great depth among the vessels and nerves of the fore-arm.
The same principles apply to the diagnosis and treatment of superficial and deep-seated abscesses. The superficial abscess is less cir cumscribed; the matter is diffused without. limit through the subcutaneous tissue ; from its position the absorption of the superincum bent tissues takes place rapidly, the skin either giving way entirely without the aid of the surgeon, or else pointing at some particular spot indicates where the abscess lancet may be employed with advantage.
The sub-fascial abscess, on the contrary, pro ceeds slowly in many eases, and even insidiously, bound down by the unyielding fascia ; it tells us of its presence, in the first instance, rather by die constitutional disturbance which it rouses than any striking indications of local mischief. These abscesses are occasionally the consequence of inflammation commencing in the theca of the flexor tendons, and the bur rowing of the matter upwards in the course of the tendons. The septa of the fascia, which have been described passing down between the muscles to the bone, limit the passage of the pus in different directions.
The fascia itself is not much subject to disease, though it seems peculiarly disposed to slough as a consequence of phleg,monous ery sipelas.
Vcsscfs.—The main arteries of the fore-arm are the radial and ulnar, into which the brachial artery divides just below the bend of the elbow. The brachial artery at this spot has on its outer side the tendon of the biceps ; on its inner side, one of the verve comites, the median nerve, and the pronator radii teres muscle. • Behind the brachial artery is the hrachialis antieus muscle, and in front of it the fascial insertion of the biceps muscle.