652 NERVES OF THE UPPER LIMB. 



inclines backwards by the side of the first phalanx of the finger, and, after 

 joining the dorsal digital nerve, ends in the integument over the last 

 phalanx. 



Fig 432 Fi" 432. DISTIUBUTION OP THE DIGITAL NERVES (from Hirschfeld and 



Leveille). 4 



1, palmar collateral nerve ; 2, its final palmar distribution ; 3, its 

 dorsal or ungual distribution, and between these numbers the network of 

 terminal filaments ; 4, collateral dorsal nerve ; 5, uniting twigs passing 

 between the dorsal and palmar digital nerves. 



Summary. The median nerve gives cutaneous branches to 

 the palm, and to several fingers. It supplies the proiiator 

 muscles, the flexors of the carpus and the long flexors of the 

 fingers (except the ulnar flexor of the carpus, and part of the 

 deep flexor of the fingers), likewise the outer set of the short 

 muscles of the thumb, and two lumbricales. 



Some similarity will be observed between the course and 

 distribution of the median and ulnar nerves. Neither gives 

 any offset in the arm. Together they supply all the muscles 

 in front of the forearm and in the hand, and together they supply the 

 skin of the palmar surface of the hand, and impart tactile sensibility to all 

 tho fingers. 



MUSCULO-SPIRAL NERVE. 



The musculo-spiral nerve, the largest offset of the brachial plexus, 

 occupies chiefly the back part of the limb, and supplies nerves to the ex- 

 tensor muscles, as well as to the skin. 



Arising behind the axillary vessels from the posterior cord of the brachial 

 plexus, of which it is the principal continuation and the only one prolonged 

 into the arm, it soon turns backwards into the musculo-spiral groove, and, 

 accompanied by the superior profunda artery, proceeds along that groove, 

 Vet ween the humerus and the triceps muscle, to the outer side of the limb. It 

 then pierces the external intermuscular septum, and descends in the interval 

 between the supinator longus and the braohialis anticus muscle to the level of 

 the outer condyle of the humerus, where it ends by dividing into the radial 

 and posterior interosseous nerves. Of these, the radial is altogether a cuta- 

 neous nerve, and the posterior interosseous is the muscular nerve of the back 

 of tho forearm. 



The branches of the musculo-spiral nerve may be classified according as 

 they arise on the inner side of the humerus, behind that bone, or on the 

 outer side. 



A. Internal branches : 



(a) Muscular branches for the inner and middle heads of the triceps. That for 

 the inner portion of the muscle is long and slender; it lies by the side of the ulnar 

 nerve, and reaches as far as the lower third of the upper arm. One branch, previously 

 noticed by authors, but more particularly described by Krause, is named by him the 

 ulnar collateral branch.. It arises opposite the outer border of the latissimus dorsi 

 tendon, and descends within the sheath of the ulnar nerve, through the internal 

 intermuscular septum, and is distributed to the short inferior fibres of the triceps 

 (Reichert and Du Bois Reymond's Archiv. 1864). 



(b) The internal cutaneous branch of the musculo-spiral nerve, commonly united in 

 origin with the preceding, winds backwards beneath the intercosto-humeral nerve, 

 and after supplying filaments to the skin, ends about two inches from the olecranon ; 



