CHAPTER VII 



THE NERVES 



The nerves which supply the fore Hmb are given off from the brachial 

 plexus. This is formed by the inferior primary divisions of the sixth, 

 seventh, and eighth cervical and the first and second dorsal nerves. The 

 w^hole of each of these primary divisions is not, however, expended in 

 forming the plexus. The division of the sixth cervical sends quite a 

 slender contributory filament. The divisions of the seventh and eighth 

 cervicals pass to it in their entirety, with the exception of the small 

 branch which each gives off to the sympathetic cord. The whole of the 

 first dorsal root runs to the plexus excepting two slender filaments, one 

 of which is its contribution to the sympathetic and the other is an 

 intercostal branch, but in the case of the second dorsal nerve we have a 

 large intercostal nerve in addition to a communicating filament to the 

 sympathetic, detached before the nerve passes to the plexus. 



The dorsal roots of the plexus turn round the anterior border of the 

 first rib near its upper extremity, where the bone presents a smooth 

 impression indicating the position of the nerves. Here they meet with 

 the cervical roots and form a flat band which passes out between the 

 superior and inferior divisions of the scalenus muscle. The relation of 

 the roots of the plexus to the first rib is important, and will be again 

 referred to in dealing with radial paralysis ; and it should be noted that 

 the posterior border of the fasciculus bends round the rib, and the 

 vertebral artery and vein are related here to its deep fiice. 



