DORSAL NERVES. 517 



near it piercing the brachial aponeurosis about the middle of 

 the arm. Above the elbow it divides into an Internal branch, 

 which proceeds over the Basilic Vein, and separates^into 

 branches that pass down on the side of the fore-arm ; and an 

 External Branch that passes under the Median Basilic Vein, 

 and continues down on the anterior part of the fore-arm. 

 There is a long and delicate nerve usually seen on the .inner 

 side of the one just described, called the nerve of Wrisberg, 

 or the lesser internal cutaneous. It usually arises from the 

 common trunk of the last cervical and first dorsal, but is 

 variable in its origin. It sends branches to the inner and front 

 side of the arm as far down as the elbow joint. It anastomoses 

 with the first intercosto-humeral in the axilJa, and with the 

 internal cutaneous, and spiral cutaneous at the elbow. 



The Articular or Circumflex 



Nerve proceeds backwards from the plexus, between the 

 teres major and minor, and passes nearly around the body of 

 the os humeri with the posterior circumflex artery, at a small 

 'distance below the head of the bone. It is distributed to the con- 

 tiguous muscles, viz. the subscapularis, teres minor and major, 

 latissimus dorsi and dehoid, and to the articulation ; but its prin- 

 cipal branches terminate in the deltoid muscle. Some branches 

 pierce the deltoid, become cutaneous and are distributed to the 

 integuments of the shoulder. 



The Dorsal Nerves 



Proceed from the cavity of the spine between the dorsal ver- 

 tebrae. They are sometimes called Intercostals, because their 

 anterior branches pass between the ribs, like the blood-vessels 

 of that name. There are twelve pairs of them, and they are 

 named numerically, beginning from above. 



These nerves proceed from the medulla spinalis by two 

 fasciculi of fibres one from each of its lateral portions the 

 posterior fasciculus is the largest. After passing through the 

 lateral foramen and the dura mater, a ganglion is formed by 

 the posterior fasciculus: the anterior fasciculus unites to the 

 VOL. ii. 44 



