HISTORY OF EXDOCKINE DOCTRINE 



The difference between the two autonomic nervous systems and the 

 central (cerebrospinal) system is that, in the former, the nerve fibers never 

 proceed, as ordinarily, directly from the nerve center to the organ con- 

 trolled, but pass, as neurons, from the gray substance to a ganglion, in 

 which they encounter a break or synapse (separating surface), on the other 

 side of which a similar post-ganglionic neuron proceeds to the organ con- 

 trolled. The synapse, a term first proposed by Sir Michael Foster, has 

 been likened to a switch, over 

 which the nervous impulse 

 jumps to proceed on its way. 

 J. N". Langley, the original in- 

 vestigator of the autonomic 

 systems, discovered that wher- 

 ever there is a switching of the 

 nervous impulse across a syn- 

 apse, the effect can be abolished, 

 in other words the post-gangli- 

 onic fiber can be paralyzed, by 

 painting over the exposed gan- 

 glion with nicotin solution, thus 

 determining whether or not an 

 autonomic nerve fiber passes 

 through a ganglion without in- 

 terruption. If, after painting 

 the exposed ganglion with di- 

 luted 0.5 nicotin solution, or 

 even after internal administra- 

 tion of the alkaloid, the effect 

 of central excitation of the post- 

 ganglionic fiber at the ganglion 

 is the same as ordinarily, then 

 there is no interruption; but, 



if the effect is abolished under these conditions, then the preganglionic 

 fiber terminates in a synapse. Langley's nicotin effect holds good 

 for all ganglia of the autonomic systems, whether of sympathetic or 

 vagal origin. In other respects, however, these two systems are 

 antagonistic, both in respect of physiological functions and response to the 

 action of drugs. The effect of electrical stimulation of a sympathetic 

 fiber is just the opposite of that of a vagal autonomic fiber. The sympa- 

 thetic fibers check, the vagal autonomic fibers excite, the movements of 

 the intestines ; the sympathetic fiber dilates, the vagal autonomic contracts, 

 the pupil ; the sympathetic hastens, the vagal autonomic slows, the heart. 

 Epinephrin, which the Viennese clinicians assume to be the specific hor- 

 mone of the sympathetic autonomic, produces, on ingest ion or injection, 



Fig. 14. John Newport Langley 



