1 86 



THE NERVOUS SYSTEM 



highest white ramus (T. i or T. 2, as the individual case may 

 be). It follows, therefore, that in complete lesions of the spinal 

 medulla above the first thoracic segment, the whole of the 

 sympathetic system is cut off from the controlling influence of 

 the cerebral cortex. 



FIG. 75. Diagram of the Sympathetic Nervous System. 



Efferent fibres from the spinal medulla to the sympathetic are shown in blue. 

 Afferent sympathetic fibres are shown in red. 



1. Afferent sympathetic fibres. 



2. Efferent sympathetic fibres. 



3. Posterior nerve-root of T. 2. 



4. Anterior nerve-root of T. 2. 



5. Efferent sympathetic fibres ascending 



cervical part of sympathetic trunk. 



6. Grey ramus communicans. 



7. Inferior cervical ganglion. 



8. Cardiac branch from 7. 



9. White ramus communicans. 



TO. Anterior ramus (primary division) 

 ofT.2. 



In the cervical region, the sympathetic ganglia are three in 

 number. The superior cervical ganglion communicates with the 

 upper four cervical nerves by means of grey rami communicantes. 

 It distributes branches to all the blood-vessels, sweat glands, 

 salivary glands, etc., of the head and neck. Some of these 

 branches issue from the upper end of the ganglion and enter 



