THE SYMPATHETIC SYSTEM. 



213 



devised. It is also uncertain as yet whether these fibers run from 

 one of the chain ganglia to a more peripheral gangUon or from a 

 more peripheral to a more proximal gangUon. The important 

 question regarding these endings is whether the visceral excitatory- 

 chain consists of more than two Unks. The physiologists claim 

 that only one sympathetic cell intervenes in any case between 

 the efferent cerebro-spinal fiber and the muscle or gland innervated. 

 The existence of sympathetic endings in sympathetic gangUa, if 

 clearly established, would seem to show that in some cases two 

 such neurones enter into the excitatory chain. 



(4) Sympathetic sensory cells. Certain cells in the peripheral 

 gangha, as in Auerbach's plexus, have longer dendrites than 

 those of ordinary sympathetic cells and these dendrites are sup- 

 posed to be distributed to the mucosae and to serve as sensory 

 fibers. The neurites of these cells pass through one or more 

 sympathetic gangha to which they give branches. These branches 



_^ Symp. g. 



Preg. fiber 



^^^-T-^ 



Inf. mes.gangr"^-'^^ — rrr 



Postg. fiber 



Fig. no. — A diagram to illustrate Langley's "axone reflex". After Langley. 

 Preg. fiber, preganglionic fiber; Postg. fiber, postganglionic fibers; Inf. mes. gang., 

 inferior mesenteric ganglion; b, bladder. 



enter into the plexus of dendrites in the gangHon and may serve 

 to arouse peripheral reflexes by stimulating the excitatory cells 

 in the ganglion. It is stated as probable (Dogiel) that these 

 neurites run on through the gray rami communicantes and form 

 the pericellular endings which are known to occur in the spinal 

 ganglia of several classes of vertebrates. These are complex 

 endings immediately around the bodies of certain spinal gangUon 

 cells which are described as cells of type II. These second type 



