144 TEE POPULAR SCIENCE MONTHLY 



spinal axis, while themselves controlling all organs containing unstriped 

 muscle, secreting glands or both, e. g., the smooth muscle of the bronchi, 

 stomach, intestines, blood vessels, genitalia, eye and all the glands of 

 external and internal secretion. The sympathetic or visceral nervous 

 system has also been called the "vegetative" system, because the 

 organs under its dominion functionate involuntarily or unconsciously, 

 as with vegetables or plants. At present, the term " vegetative system," 

 formerly termed the autonomic system by Langley, is restricted to that 

 part of it which originates from the sympathetic ganglia, while the 

 antagonistic system governing involuntary muscle, which is largel;^ 

 made up of fibers from the vagus nerve, is now styled the "vagal 

 autonomic." 



The difference between the two autonomic nervous systems and the 

 central (cerebro-spinal) system is that, in the former, the nerve fibers 

 never proceed, as ordinarily, directly from the nerve center to the 

 organ controlled, but pass, as neurons, from the gray substance to a 

 ganglion in which they encounter a break or synapse (separating sur- 

 face), on the other side of which a similar post-ganglionic neuron pro- 

 ceeds to the organ controlled. 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. Langley, the original inves- 

 tigator of the autonomic systems, discovered that wherever there is a 

 switching of the nervous impulse across a synapse; the effect can be 

 abolished in other words the post-ganglionic fiber can be paralyzed, by 

 painting over the exposed ganglion with nicotine solution, thus deter- 

 mining whether an autonomic nerve fiber passes through a ganglion 

 without interruption or not. If, after painting the exposed ganglion 

 with diluted 0.5 nicotine solution, or even after internal administration 

 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 inter- 

 ruption; but if the effect is abolished under these conditions, then the 

 pre-ganglionic fiber terminates in a synapse. Langley's nicotine effect 

 holds good for all ganglia of the autonomic systems, whether of sympa- 

 thetic 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 sympa- 

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

 sympathetic fibers check, the vagal autonomic fibers excite, the move- 

 ments of the intestines; the sympathetic dilates, the vagal autonomic 

 contracts, the pupil ; the sympathetic hastens, the vagal autonomic slows, 

 the heart. Adrenalin (epinephrin), which the "Viennese clinicians as- 

 sume to be the specific hormone of the sympathetic autonomic, produces, 

 on ingestion or injection, effects similar to those produced by electrical 



