Chap. xx.] THE SYMPATHETIC SYSTEM. 



169 



or multi-polar. The cell is invested in a capsule lined 

 with nucleated cells, both being continued on the pro- 

 cesses as neurilemma and nerve corpuscles respectively. 

 The processes of the ganglion cells are all axis 

 cylinder processes, and invested in the neurilemma, 

 thus representing non-medul- 

 lated nerve-fibres. They do not 

 become as a rule medullated. 



225. In the frog (Beale, 

 Arnold) and also in some few 

 instances in the mammal, the 

 sympathetic ganglion cell gives 

 off one straight axis cylinder 

 process, into which the sub- 

 stance of the ganglion cell is 

 prolonged. This is entwined 

 by a thin spiral fibre (Fig- 100), 

 taking its origin by two or 

 more rootlets from the ganglion 

 cell substance, and circling 

 round the (thicker) straight 

 axis cylinder process. A single 

 neurilemma ensheathes them 

 both. Soon the spiral fibre 

 leaves the axis cylinder process, 

 becoming invested with a 

 medullary sheath and its own 

 neurilemma, thus forming a 

 medullated fibre, whereas the 

 straight axis cylinder continues 

 its course as a non-medullated 

 nerve-fibre (Key and Retzius). 



226. The ganglia in connec- 

 tion with the plexuses of nerve 

 branches of the heart, the 



ganglia in the plexus of non-medullated nerve-fibres 

 existing between the longitudinal and circular coat 



Fig. 100. A Sympathetic 

 Ganglion Cell of the Frog, 

 showing the straight pro- 

 cess and the spiral fihre ; 

 the latter becomes a me- 

 dullated fihre. (Key and 

 Ketzius.) 



