HISTORY OF THE INVOLUNTARY NERVOUS SYSTEM 17 



of opinion that all these vagrant sympathetic ganglia gave origin 

 to efferent nerve fibres and none of them to afferent, I did not 

 attempt to decide the question. Undoubtedly a certain number 

 of the medullated fibres of the ramus communicans pass towards 

 the cord into the posterior root ganglion and so into the posterior 

 roots, the proportion of these to the motor fibres in the same 

 ramus differing largely in different nerves. Thus the white rami 

 which form the nervus erigens contain, according to Langley and 

 Anderson, as many as \ afferent fibres and only efferent, while 

 in the hypogastric nerve the respective numbers are as I to 10. 



Sections of the posterior roots however give no such striking 

 picture as in the case of the anterior roots ; for it is not possible 

 to distinguish by differences of structure in the posterior roots 

 the distribution of the white rami communicantes. Fine medul- 

 lated fibres were much more universally to be found in all these 

 roots, no matter where they were situated. Langley has, I 

 think, settled this question definitely by the method of degener- 

 ation. If sensory cells exist in the lateral chain of ganglia, then 

 sections of the ramus communicans, after time allowed for de- 

 generation, must show the presence of degenerated fibres in the 

 part still in connexion with the spinal nerves ; and similarly 

 sections of the " rami efferentes" should show the presence of de- 

 generated fibres in their ends, which appear to spring from the 

 lateral chain, if their nutrient centres were in cells of the collateral 

 ganglia. In neither case is there any evidence of degeneration. 

 All the afferent fibres have their nutrient centres in the posterior 

 root ganglia. No peculiarity therefore exists on the afferent side ; 

 the course of the sensory fibres is the same in all sensory nerves, viz. : 

 direct to the cells of the posterior root ganglia with no connexion 

 with any cells in sympathetic ganglia. Seeing then that all the 

 fibres entering into the posterior root ganglia are medullated, it 

 follows that all non-medullated fibres are efferent, none afferent, 

 and that the so-called sympathetic system is not a complete central 

 nervous system, but consists purely of excitor neurons. 



As already stated, these motor nerve cells and the sensory 

 nerve cells at one period formed a single mass of cells in the 

 position of the posterior root ganglion, and then, as growth went 

 on, the motor or sympathetic mass separated off and became more 

 and more vagrant, while the sensory mass remained stationary 

 just outside the spinal cord. A reminiscence of the original state 



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