748 



THE NERVES. 



Fig. 346. 



voluminous trunks, as may be remarked in those proceeding from tie two 

 enlargements (or bulbs) of the spinal cord. The common axis of these two 

 fasciculi affects a transverse direction in nearly all the spinal pairs ; but 

 that of the posterior nerves inclines more backwards as they reach the 

 terminal extremity of the cord. 



The filaments of the superior fasciculi, or sensitive roots, are larger than 

 the others, and emerge from the collateral sulcus of the spinal cord. They 

 may be followed to the cells of the superior grey cornua. 



The filaments of the inferior fasciculi, or motor roots, arise opposite 

 to the preceding, on the lower face of the cord, at a short distance from tlie 

 middle line, and on the limits of the inferior and lateral columns. They may 

 also be traced to the interior of the cord, as far as the inferior grey cornua. 



These filaments do not unite to form their common trunk until after 

 they have passed through the dura mater ; this is an extremely short trunk 

 that occupies the corresponding intervertebral foramen, and presents on its 

 upper face a ganglionic enlargement, which is exclusively placed on the 

 course of its sensitive fibres ; the motor filaments being simply laid 

 beside them, and do not mix with them until beyond 

 the ganglion. Immediately after this union, a small 

 filament is given off that enters the spinal canal to 

 be distributed to the sinuses and the vertebrae. 



After leaving the meningeal sheath, the radicular 

 fasciculi of the nerves furnished by the terminal ex- 

 tremity of the spinal cord, run a somewhat long 

 course in the sacral canal, before finally uniting and 

 jaassing into the tissues ; the common fasciculus they 

 collectively form at the posterior extremity of the 

 spinal canal is named the cauda equina. 



The distributive branches of the spinal nerves 

 cannot be considered in a general manner, because of 

 their diversity. We will study them successively in 

 each region of the spine. 



Article I. — Cervical Neetbs (8 Pairs). 



SuPERioB BitANCHES. — The first passes through 

 the superior foramen of the atlas, in company with 

 the cerebro-spinal artery. It arrives in the inter- 

 stice between the small oblique muscle of the head 

 and the posterior straight muscles, and divides imme- 

 diately into several divergent branches which are 

 distributed to the three above-named muscles, the 

 anterior extremity of the great complexus, and the 

 cervico- and temporo-auricular muscles. The ramus- 



those coming from the cule sent to the latter ascends within the concha, and 



ganglion , d, Superior breaks up into several filaments that supply the skin 



trunk of Bpmal nerve ; f ^j^ external ear. 



c, Its inferior trunk. _,, ,7 ■,. , , 



ihe second immediately furnishes some ramus- 

 cules to the great oblique muscle, beneath which it is placed, as well as to 

 the small oblique. It is afterwards directed backwards, comporting itself 

 like the succeeding ones. 



These diminish in volume from the third to the eighth. All pass 

 through the intertransversales-colli muscles, and divide into several 



GANGLION OF A SPINAL 

 NERVE FROM THE LUM- 

 BAR REGION OF A 

 PUPPi". 



u, Superior root; h, In- 

 ferior root ; c, Ganglion 

 on the superior root ; 

 d, e. Junction of the 

 fibres from the inferior 

 and superior roots with 



