396 OKIGIKAX ABTICLES. 



show how closely anterior and posterior roots are connected, and how 

 nearly they come to having a common origin." 



Van der Kolk gives drawings of the connections of the fibres of 

 nerve roots with the multipolar cells, which, he says, he has repeatedly 

 succeeded in tracing, although owing to the fibres not pursuing a 

 perfectly straight course, they are often cut through in making 

 sections of the cord. " There can be no doubt," he remarks, " that 

 the roots of the motor nerves arise from the spinal cord, and more 

 particularly from the ganglionic cells of the anterior horns," The 

 investigation of the connection of posterior roots with the cells. 

 Van der Kolk has found more difficult ; he has traced them into the 

 horn proceeding towards the cells, but their minuteness has prevented 

 his seeing whether they absolutely pass into the cell. A portion of 

 the posterior roots, viz : those for sensation, are however subsequently 

 described by Van der Kolk as passing, immediately after their entrance 

 into the spinal cord, upwards along the posterior columns in order 

 to repair to the brain, or seat of perception. They do not penetrate 

 the grey matter, while the rest of the posterior roots, or those for 

 reflex action, are said by him to go to ganglionic ceUs of the posterior 

 iiorns. These distinctions however are theoretical, not anatomical. 



Stilling lays it down as the general role that the nerve-roots 

 pursue an apparently unbroken course of nerve fibrils from the cord, 

 but not always preserving the same plane. Spaces entirely free 

 from fibres between two neighbouring nerve-roots are rarely met 

 with. 



Dr. Brown-S^quard (of whose philosophical researches a lucid 

 exposition was given in a previous number of this journal) also 

 expressly states that he has fomid the " nerve-fibres of the spinal 

 nerves, after they have entered the grey matter, attaching them- 

 selves to the nerve-cells." 



Measueements. 

 Cells in grey matter 



Width f ^^ to -j^ In. 



f -JL_ 



^ , J 2 90 



Length ? ^4-^ to ^- 



JNuclei 01 cells . . _j._ to v-r--^ 



Processes of ceUs . . -^^ to j^l- 



Nerve-fibres in longit. cols. -g\\ to -g^-^ 



in roots - J^^ to ^^^ 



Gelatmous subst. ^-i^- to -j^^^ 



Commissural gJ-,^ to -^^-^ 



Blood-vessels . . _i- to ^oioo 



The above measurements represent the average dimensions of the 

 several structures, but do not affect to indicate their minimum or 

 maximum. 



