THE CIRCUMFLEX NERVE. 



295 



furnishes the nerve to the teres minor, on which there is often a small reddish 

 enlargement. It then turns round the posterior border of the deltoid below the 



Fig. 195. DISTRIBUTION OP THE POSTERIOR CUTANEOUS NERVES OF THE 

 SHOULDER AND ARM (Hirsclifelcl and Leveille. ) I 



1, supra -acromia) branches of the cervical plexus descending on the 

 deltoid muscle ; 2, ascending and 2', descending cutaneous branches of 

 the circumflex nerve ; 3, inferior external cutaneous of the musculo- 

 spiral nerve ; 4, posterior cutaneous branches of the musculo-cutaneous 

 nerve to the forearm ; 5, 6, internal cutaneous of the musculo- spiral ; 

 7, nerve of Wrisberg ; 8, 9, posterior branches of the internal cutaneous 

 nerve. 



middle, and ramifies in the integument over the lower two- 

 thirds of that muscle, and over the adjacent part of the 

 triceps (n. cutaneus Irachii lateralis). 



(c) One or two articular filaments for the shoulder- 

 joint arise near the commencement of the nerve, and 

 enter the capsular ligament below the subscapular muscle. 



Rauber describes a filament of the upper branch as ascending 

 in the bicipital groove to be distributed to the upper extremity of 

 the humerus and the capsule of the shoulder- joint. 



Varieties. The circumflex nerve is occasionally derived wholly 

 from the fifth cervical ; and the contribution from the sixth 

 nerve is often very small. It has been seen to perforate the lower 

 part of the subscapularis muscle (Macalister, Bubenik), to which 

 it often furnishes a branch. Branches to the long- head of the 

 triceps and to the infraspinatus are also mentioned. 



Internal cutaneous nerve. The internal cutaneous 

 nerve (n. cutaneus antibrachii medialis) is composed of fibres 

 proceeding from the first dorsal, and usually also from the 

 eighth cervical nerve. After leaving the inner cord of 

 the plexus, it is placed at first to the inner side of the 



axillary artery, and then descends superficially between the brachial artery and the 

 basilic vein to rather below the middle of the arm, where it becomes subcutaneous. 

 As it pierces the fascia it is divided into two parts, one destined for the anterior, 

 the other for the posterior surface of the forearm. 



(a) The anterior division crosses at the bend of the elbow behind (less frequently 

 over) the median-basilic vein, and distributes filaments in front of the forearm, as 

 far as the wrist ; one of these may be joined with a cutaneous branch of the ulnar 

 nerve (fig. 197, 14). 



(b) The posterior division, smaller than the anterior, inclines to the inner side 

 of the basilic vein, and sends its branches obliquely backwards round the inner 

 margin of the forearm to supply the skin about as far as the subcutaneous border of 

 the ulna. Above the elbow this division is connected with the small internal 

 cutaneous nerve ; in the forearm it communicates with the anterior part of the 

 internal cutaneous, and near the wrist sometimes with the dorsal branch of the 

 ulnar nerve. 



(c) One or more branches to the integument of tlie arm pierce the fascia near the 

 axilla, and reach to the elbow, or nearly so, distributing filaments outwards over the 

 biceps muscle. 



Varieties. The posterior division of the internal cutaneous nerve has been seen arising 

 separately from the posterior branch of the lower trunk of the brachial plexus (G-. Elliot 

 Smith, Journ. Anat.. xxix, 85). Cases are recorded in which the posterior division is joined, 



