THE SPINAL NERVES. 



179 



.3 



The sheath contains nerve-cells and Fi g- I1 9- 



fibres, and sends in a few fine processes to 

 support these structures. The fibres of 

 the posterior root enter and pass out of 

 the gang-lion without suffering any 

 changes, except that the nerve fibres are 

 slightly separated by the presence of a 

 few nerve-cells, and that a distinct in- 

 crease in the number of nerve fibres takes 

 place. The nerve-cells, of which the 

 ganglion is chiefly composed, and upon 

 the number of which its size directly de- 

 pends, are arranged chiefly around the 

 fibres of the dorsal root ; such few as 

 lie between the fibres are smaller than 

 the rest and vary more in their relative 

 numbers ; at times one or two isolated 

 cells are found in the capsule or even in 

 the adjoining ' periganglionic gland/ 

 The cells near the capsule are somewhat 

 smaller than the deeper cells 1 . Each of 



\entral view of the spinal ganglia ; 



these cells, which are usually pear-shaped, on the right side they are sun 



1 ".-i 11 hidden by the ' periganglionio 



possesses only one process ; the cell mem- 



Fig. 1 20. 



brane is thick, resistant, and possessed of 



an external nucleated, endothelial covering, the space around 



being probably a pericellular lymph-space ; it often contains one to 



three small fat-globules ; the protoplasm 



of these has. according to v. Lenhossek. 



a concentric fibrillation ; the nucleus is 



round, clear, and distinct, and relatively 



larger the smaller the nerve-cell ; it is 



usually placed in the centre of the cell. 



In that portion of the cell towards the 

 process is a portion brighter and less 

 easily stained than the rest of the cell 

 (Polarkernen, Courvoisier); this apparent- 

 ly posseec - one or two nuclei, and is 

 regarded as a cell by Lenhossek (Polar- 

 zellen); the process of each cell soon 

 acquires a medullated sheath, and after 



1 Larger cells of deeper layer 80 /j. to 90 fj. in diameter, sometimes one or two as 

 large as c-i mm. v. Lenhossek. 



X 2 



Schenia^pf spinal ganglion. 



A Ventral root. 



' ' Ramos communicant. 



G Ganglion. 



Dorsal division. 



P Dorsal root. 



J{ Ventral division. 



