KESTEVEN ON THE ANATOMY OP THE SPINAL COED. 395 



large number diverge equally dowmoards and upwards, for some 

 distance in the grey substance, while the remainder pass more deeply 

 backwards and are lost. In no single instance has the author seen 

 any portion of these roots take a longitudinal course on directly 

 entering the anterior white cohnnns. 



" But besides the transverse bundles which form the anterior roots, 

 a continuous system of exceedingly fine transverse fibres may be 

 seen to issue from the anterior grey substance. They pass through, 

 nearly aH at right angles to, the anterior white columns, and disappear 

 as thoy proceed towards the surface of the chord ; but as many of 

 them may be observed to turn round and take a longitudinal 

 direction, it is probable that at the points where they disappear they 

 all follow the same course. Within the grey substance they wind 

 about and are gradually lost, mingling with the fibres of the anterior 

 roots, and with those proceeding from the fine bundles of the posterior 

 roots, which, perhaps, are continuous with them. 



" It may then, Mr. Clarke adds, be fairly laid down as a well 

 established fact, that nearly all, if not the whole of, the fibres com- 

 posing the roots of the spinal nerves, after passing through the 

 anterior and posterior white columns of the chord, proceed at once 

 to its grey substance ; and that if any of them ascend direct It/ to the 

 brain, it must be tJiose only of the posterior roots which run longitu- 

 dinally in the posterior columns." 



The connection of the nerve roots with the cells is established 

 uj repeated observations of the majority of observers, although it is 

 not equally certain that all the nerve roots are derived from cells ; 

 many fibres of the anterior roots, for instance, being continuations 

 of fibres from posterior roots. 



*" It appears that there are probably, as regards origin, the 

 three following classes of nerve roots, viz :— 



1st. (a) Anterior roots which arise from or terminate in anterior 

 cells. 

 (b) Posterior roots which arise from or terminate in posterior 

 cells. 



2nd. Anterior and Posterior roots which meet in cells in the 

 central part of the chord. 



3rd. Anterior and Posterior roots which are directly continuous, 

 i.e. unconnected with any cells in the chord. 



" The first class consists of nerve roots which are united, if at all, 

 through medium of deeper lying cell-groups, those of the last two . 

 classes being more directly continuous. I am, however, very far from 

 intending to imply any supposed diflference of function between 

 these classes, for I am very strongly convinced that the function of 

 cell anrl fibre is every where the same ; and one of the principal 

 objeeti I have had in view in the above classification has been to 



• Dean, p. 10. 

 N. H. R.— 1862. 2 E 



