CHAPTEK XXI. 



The PERIPHBEAL-lSrERTB KOOTS, THE SPINAL GaNGLIA, AND THE 



Spinal Coed. 



The peripheral nerves, as is well known, contain both motor and sen- 

 sory fibers. Near to the spinal cord these separate from each other. The 

 motor division enters the cord directly as the anterior root. The sensory 

 fibers enter the spinal ganglion. 



In the spinal ganglia there are large cells, which sometimes give ofE 

 two processes, but usually only one. If there is but one, it divides soon after 



Fig. 213. — Scheme of the relationships between the spinal cord and the 

 nerve-roots. Tordere Wurzcl, Anterior root. Hint. ll'/nveZ, Posterior root. Mot. 

 Tliiil, Motor portion. Sens. Thcil, Sensory portion. Gemischter Ncri\, Mixed 

 nerve. 



leaving the cell-body into two; so that, in the end, it amounts to practically 

 two cell-processes. 



It will be remembered that, according to the observations of His, the 

 sensory nerves grow out from these cells as peripheral processes, but that 

 these cells also send one process into the spinal cord, a bundle of such proc- 

 esses constituting the posterior root. 



Since, according to actual count, the posterior roots contain approxi- 

 mately the same number of fibers in the adult as the nerves just beyond the 

 ganglia, it would seem that there were simply an interposition of a cell in the 

 course of every such fiber. 



(332) 



