426 



THE CENTRAL NERVOUS SYSTEM. 



the neurilemma of the single process. (2) Type II spinal ganglion 

 cell of Dogiel. Dogiel has recently described a second type of spinal 

 ganglion cell which differs materially from the type just described. 

 The cell-bodies of these neurones resemble closely those of the typ- 

 ical spinal ganglion neurones. Their single medullated processes 

 divide, however, soon after leaving the cells into branches which 

 divide further and which do not pass beyond the bounds of the gan- 

 glia but terminate, after losing their medullary sheaths, in compli- 

 cated pericapsular and pericellular end-plexuses surrounding the 

 capsules and cell-bodies of the typical spinal ganglion cells. (3) Mul- 

 tipolar ganglion cells ; in nearly all spinal and cranial ganglia there 

 are found a few multipolar nerve-cells, which in shape and struc- 

 ture resemble the nerve-cells of the sympathetic system. 



Fig. 340. Diagram showing the relations of the neurones of a spinal ganglion ; 

 p. r., posterior root; a. r., anterior root; /. s., posterior branch and a. s., anterior 

 branch of spinal nerve ; w. r., white ramus communicans ; a, large, and 6, small spinal 

 ganglion cells with T-shaped division of process ; c, type II spinal ganglion cells (Dogiel); 

 s, multipolar cell ; d, nerve-fiber from sympathetic ganglion terminating in pericellular 

 plexuses (slightly modified from diagram given by Dogiel). 



Entering the spinal ganglia from the periphery are found a rel- 

 atively small number of small, medullated or nonmedullated nerve- 

 fibers, probably derived from sympathetic ganglia. These nerve- 

 fibers, medullated and nonmedullated, the former losing their 

 medullary sheaths within the ganglia, approach a spinal ganglion 

 cell, and after making a few spiral turns about its process, termi- 

 nate in pericapsular and pericellular end-plexuses. Dogiel believes 

 that the cell-bodies and capsules thus surrounded by the terminal 

 branches of the sympathetic fibers terminating in the spinal ganglia 

 belong to the spinal ganglion cells of the second type first described 

 by him. In figure 340 is represented by way of diagram the 

 structure of a spinal ganglion. 



In the medium-sized cells (from 30 fJ. to 45 fj. in diameter) of the 



