THE NERVOUS SYSTEM. 



405 



my " Microscopical Anatomy," 116. The roots are furnished with a 

 delicate neurilemma, derived from the pia mater, and presenting a simi- 

 lar structure, which forms both an external sheath 0*002 of a line in 

 diameter, as well as internal septa to the individual fasciculi. The con- 

 tiguous roots frequently anastomose, and this is much more usually the 

 case with the sensitive roots ; in the cervical nerves in Man in parti- 

 cular, it is found to take place constantly in one or other of the nerves. 



120. The structure of the spinal ganglia, in the Mammalia, is a 

 difficult subject of investigation, but I think the following may be stated 

 with certainty respecting them. Fig. 154. 



The sensitive roots, so far as I 



have hitherto been able to make ^ 



out, enter into no connection 

 with the nerve-cells in the gan- 

 glion, but forming one, or, in the 

 larger ganglia, several, or even 

 numerous fasciculi, which in the 

 latter case anastomose, simply 

 traverse it, to be reunited be- 

 low the ganglion into a single 

 trunk, which is then immediate- 

 ly blended with the motor root. 

 Most of the nerve-cells them- 

 selves appear to be in connec- 

 tion with the nerve-fibres, giv- 

 ing off either one or two, or 

 more rarely, several. These 

 fibres, which I term ganglion- 

 fibres, proceed in a prepon- 

 derating majority perhaps all 

 of them peripherally, joining 

 and strengthening the perfora- 

 ting root-fibres ; so that each 

 ganglion is to be regarded 

 as a source of new nerve- 

 fibres.* 



FIG. 154. A lumbar ganglion of a young Dog, treated with soda, and magnified 45 

 diameters: S, sensitive roots; M, motor roots; R.a, anterior branch of the spinal nerve; R.p, 

 posterior branch ; in both their composition from both roots is manifest ; G, ganglion, with 

 the cells and ganglion-fibres, which assist in the strengthening of the sensitive roots travers- 

 ing the ganglion. 



* [The new " ganglion-fibres" join differently the nerve-fibres on which the ganglion is 

 seated, or by which it is perforated. In the large ganglia the new fibres penetrate in 



