'Mil \i rONOMIC NERVi M B79 



composed entirely of fibers belonging to voluntary 

 also of connector fibers of the involuntarj tem l distin- 



guished from the voluntary fibers by being much smaller in diamel 

 indeed it was by this characteristic thai Gaskell succeeded in ti 

 course of I he involuntary fibers. 



In brief, therefore, the fibers of the internuncial neuroi volun- 



tary nervous system are confined within the central ner 

 where they are contained mainly in tin 1 white columns of tin- Bpinal cord, 

 pyramidal tracts, for example, being composed of internuncial fi : 

 from the cerebral ueurons; the corresponding fibers of the involuni 



nervous system (connector), on the other hand, run oul of ti rd with 



the anterior roots to effector neurons situated either in the ganglia 

 the sympathetic chain or in peripheral localities. Jus1 ;i- the voluntary 

 internuncial fibers give off many collaterals, so do those <>t* 'he involun- 

 tary system, so thai an impulse transmitted by one internuncial neuron 

 may excite a broad field of effectors. We shall see later thai it is through 

 these collaterals that reflex responses can apparently often 

 by the stimulation of the central ends of nerves such as the hypogastric 

 tn the bladder after all connections with the central nervo 

 have been severed. Pig. 230. 



To elucidate the further coursi of the involuntary fibers, and d 

 mine the location of the effector neuron nerve cells, it becon • 3ary 



to supplement anatomical with physiological methods of investigation, 

 various functions of the innervated parts ascular changes, muscular 

 movements, glandular activity are observed by the usual methods 

 the physiologist, and the nerve mots or nerves believed to contain 

 involuntary fibers either cu1 or stimulated. It' a change is ol i in 



the functions, it indicates that part at least of the involuntary net 

 supply is contained in the nerve structure that has been cul of stimu- 

 lated. Such a resull does not. however, inform us a- \>> whethei 

 fiber is that of the connector or effector neuron whether it is 

 ganglionic or postganglionic. This may he determined in man;. 

 by observing whether nerve degeneration occu 

 the fibers, hut the most useful method for answering th( 



that discovered h\ Langlej by the use of nicotine, which ii 



cent rat ions specifically paralyzes the synaptic 



connector and the effector neurons. IT a weak I 



this alkaloid is painted on a ganglion or peripheral • • in 



which the connector neuron finds its effector tie ill hn 



the nerve path, so thai physiological responses produced l»> stinm 



the preganglionic fibers become no longer elicitabh w '"• 



tary connector fibers run through Beveral 



