CH. XIV.] 



SPINAL NERVE ROOTS 



157 



sympathetic system with which they communicate. The recurrent 

 sensory fibres in this root do not 

 degenerate with the others, but 

 are found degenerated in the 

 part of the anterior root at- 

 tached to the spinal cord. 



Section of the posterior root 

 always produces the same phy- 

 siological effect (loss of sensa- 

 tion)* wherever the section is 

 made, but the degeneration effect 

 is different according as the sec- 

 tion is made on the proximal or 

 distal side of the ganglion. If 

 the section is made beyond the 

 ganglion, the degeneration occurs 



oo cV^-i in P Vwnrnnd fVo QAP FIG. 161. Diagram to illustrate Wallerian degene- 

 aS Snown in O Deyona ine Sec- ration of nerve-roots. 



tion in the peripheral portion of 



the posterior root-fibres ; the anterior root remains intact except for 

 the recurrent sensory fibres which it con- 

 tains. If the section is made as in D, 

 between the ganglion and the cord, the only 

 piece that degenerates is the piece severed 

 from the ganglion and running into the 

 cord; these fibres may be traced up in the 

 posterior column of the spinal cord until 

 they terminate in grey matter, which they 

 do at different levels. The whole of the 

 sensory fibres, including the recurrent ones 

 which are still attached to the ganglion, 

 remain histologically healthy. 



The accompanying figure (fig. 162) is one 

 of the original illustrations made by Dr 

 Waller, and I am indebted to the present 

 Dr Waller for permission to reproduce it. 

 These facts of degeneration teach us, 

 roots several days alter sec- what we also learn from the study of em- 



tion of both roots close to the -, ^ .-i ,i r>i n ,-t 



cord ; the anterior fibres are bryology, that the nerve-fibres of the an- 

 terior root are connected to the nerve-cells 



the nerve-ceiis from which within the spinal cord, while the posterior 



they grew, are normal. , , . . , ,-f . , , 



root-fibres are connected to the cells 01 tne 

 spinal ganglia ; or, to put it another way, the trophic centres which 



* In order to obtain any appreciable loss of motion or sensation, it is necessary 

 to divide several roots (anterior or posterior as the case may be), as there is a good 

 deal of overlapping in the peripheral distribution of the fibres. 



