HISTOR Y OF THE INVOL UNTA R Y NER VO US S YSTEM 1 9 



FIG. 4. THE ARRANGEMENT OF THE CONNECTOR FIBRES (BLACK) AND THE 

 EXCITOR NEURONS (RED) OP THE SYMPATHETIC SYSTEM IN THE SPINAL 

 REGION. 



All the spinal nerves are shown from the first cervical, C.i, to the third coc- 

 cygeal, Co. 3. 



All the connector neurons leave the spinal cord in the thoracico-lumbar outflow 

 which extends from the second dorsal, D.2, to the third lumbar, ,.3. The lateral 

 chain of sympathetic ganglia is connected together by the further prolongation of 

 these processes which run from ganglion to ganglion, connecting in three or more 

 of them with the cells of excitor neurons. The lateral chain is therefore made 

 up of a series of groups of excitor neurons connected together by the processes of 

 connector neurons. Certain ganglia have become fused, those corresponding to the 

 first four cervical nerves being aggregated into superior cervical ganglion, S.C.G., 

 those of the last four cervical and the first four dorsal being aggregated into the 

 stellate ganglion, St.G., which lies just caudal to the annulus of Vieussens, A.V. 

 For the sake of simplicity the ganglia on this annulus and the inferior cervical 

 ganglion have been omitted and considered part of the stellate ganglion. The pro- 

 cesses of the excitor neurons belonging to any ganglion run out in the grey ramus 

 communicans to join the spinal nerve and to be distributed with it. The excitor 

 fibres for the first four cervical nerves thus arise from the superior cervical ganglion, 

 S.C.G. ; the excitor neurons for the last four cervical nerves arise from the stellate 

 ganglion, St.G., and at first all run in the ramus vertebralis, R.V., they finally 

 branch from this and join their respective nerves. Similarly the excitor fibres of the 

 first four dorsal nerves all arise from the stellate ganglion, St.G., to which the first 

 three white rami communicantes run. The rest of the spinal nerves are supplied 

 with sympathetic excitor fibres from their corresponding sympathetic ganglia. 



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