750 



A TEXTBOOK OF PHYSIOLOGY 



postganglionic fibres, and are non-medullated. Those that pass back 

 to the spinal nerves form the grey rami communicantes (Fig. 459). 

 The cell-stations of the preganglionic fibres are traced by the nicotine 

 method. It is found that when a ganglion is painted with nicotine 



MID-BK/>tM AUTOfOHIC 



FIG. 4o9. THE AUTONOMIC NERVOUS SYSTEM (After Purves Stewart .) 

 A, Chromaffinic tissue yielding adrenalin; S, sympathetic ganglion. 



the preganglionic nerve endings are first stimulated and then paralyzed ; 

 when the effect of stimulation of the preganglionic nerve is abolished, 

 stimulation of the postganglionic fibres arising from the ganglion still 

 has its effect. By observing the effects of stimulation of the pie- 



