178 



THE NERVOUS SYSTEM. 



smallest. The ganglion is not attached to the dorsal root alone 

 but is prolonged a short distance beyond the point of union of the 

 two roots ; this is best seen in the nerves of the lumbar plexus. 



Each ganglion is a yel- 

 Fig. ii8 lo wish- white rounded 



or oval body, with an 

 outer thick (sometimes 

 0*15 mm. thick) sheath 

 of connective - tissue, 

 connected by the epi- 

 neurium of the nerve 

 roots with the Dura 

 mater. This sheath is 

 composed of bundles of 

 parallel, wavy, white, 

 connective-tissue fibres, 

 which enclose a large 

 number of connective- 

 tissue corpuscles, and 

 here and there contains 

 brown pigment. 



By means of longi- 

 tudinal and transverse 

 sections it may be seen 

 that the ganglion sur- 

 rounds the ventral root, 

 but that it forms a 

 thinner layer on that 

 side, where the dorsal 

 root joins the ventral ; 

 althoug-h at this point 

 the two roots and the 

 ganglion are firmly uni- 

 ted together, the thick 

 fibrous sheath of the 

 ganglion prevents any 

 communication be- 



Veiitral view of t}ie brain and spinal cord, to sliow the twCCU tllC UCrVOUS clc- 



points of exit of the spinal nerves. , p -i , ^ 



ments or the ventral 



JV/i-io Spinal nerves. 



VG Trigeminal gangUon. rOOt and thoSC of the 



Jfi-io Vertebrae. ■.. 



X(i Ganglion of vagus. gang-JlOn. 



