THE SYMPATHETIC SYSTEM 293 



from a physiological point of view to the thoracic 

 lumbar system. 



II. VEGETATIVE SYSTEM ARISING FROM THE CORD. 8 



From the point of view of vegetative centres, we must 

 divide the cord into three regions which correspond to 

 three sets of vegetative fibres. 



1. The part superior to the cervical cord (above the IV 

 cervical segment). 



2. The portion of the cord found between the two 

 following limits: 



(a) Superior limit, I or II dorsal segment. 



(6) Inferior limit, the III or IV lumbar segment. 



This region is called the thoracic-lumbar region of the 

 vegetative nervous system or true sympathetic system. 



3. The portion of the cord below the V lumbar seg- 

 ment; this is the sacral portion or pelvic segment of the 

 vegetative system. 



We shall now study each of these segments individually. 



A. MEDULLARY CERVICAL VEGETATIVE PORTION. 



The vegetative fibres which arise from this area, go up 

 towards the head by means of the medullary root of the 

 spinal nerve and with this nerve reach the vagus. 9 



B. THORACIC-LUMBAR MEDULLARY PORTION. 



From the vegetative column, formed by the superpo- 

 sition of the intermediar lateral nuclei of the anterior horn 

 of the medullary segments, arise vegetative fibres which 

 follow, first, the anterior roots, then the white rami com- 

 municant, and finally reach the sympathetic ganglia of 

 the lateral chain. We have seen how, in the simplest 

 case, these fibres end and communicate with one or more 



8 See Figs. 25 and 27. 



9 We have already studied these with the vagus. 



