524 PHYSIOLOGY 



(2) The next set of nerve fibres have their cell station in the 

 stellate ganglion. The white rami arise from the fifth to the eighth 

 thoracic nerves, while the grey rami pass to the nerve-roots from the 

 third cervical nerve to the fourth thoracic nerve. 



(3) The remaining nerves, supplying all the rest of the body 

 and tail, arise by the white rami from the seventh thoracic to the 



-Pre-ganglionic fibre 



-Symp. gangl. 



Made-up spinal nerve '' 



- Post-ganglionic fibre 



FIG. 237. Diagram (after LANGLEY) to show the manner in which a spinal nerve is 

 completed by the entry of a grey ramus, containing fibres derived from cells in 

 the sympathetic chain. 



p.pr.d, posterior primary division. (The post-ganglionic fibres are repre- 

 sented red.) 



third or fourth lumbar nerve, and are distributed as grey rami to 

 all the spinal nerves below the fourth thoracic. 



We thus see that, in speaking of the functions of a spinal nerve- 

 root, we must clearly distinguish whether we mean the root as it 

 arises from the spinal cord, in which case its visceral functions will 

 include those of its white ramus, or whether we mean the made-up 

 or complete spinal nerve after it has received its grey ramus (Fig. 237). 

 In the latter case the visceral functions of the root will be more 

 restricted than in the former case, and will have a different distribu- 

 tion. In stimulating the nerve-roots in the spinal canal it is sometimes 

 possible, by weak stimuli, to display the functions of the corresponding- 

 white ramus, and then by increasing the stimulus to get superadded 

 the effects due to the excitation of the grey ramus in the made-up 

 nerve, in consequence of the spread of current. 



" When, for example, the eleventh thoracic anterior roots are stimulated 

 in the spinal canal with weak shocks, a fairly long strip of hairs in the lumbar 



