STUDIES ON THE SYMPATHETIC NERVOUS SYSTEM 307 
indicated in the diagram; and, if so, the working out of conduc- 
tion pathways should not be as difficult as we had supposed. In 
fact, a great deal along this line has already been accomplished 
by the physiologists; but there yet remains a large amount of 
work to be done before the course of nerve impulses through the 
sympathetic nervous system can.be mapped with accuracy 
Since there is considerable confusion in the use of terms re- 
ferring to this division of the nervous system, we wish at the 
outset to define those which we shall have occasion to use. 
The sympathetic nervous system is an aggregation of ganglia, 
plexuses, and nerves through which the glands, heart, and all 
smooth muscle receive their innervation. It is a term belonging 
primarily to descriptive anatomy and includes the ganglionated 
plexuses associated with the fifth nerve and the vagal plexuses 
of the thorax, as well as the sympathetic trunk and the parts 
more directly associated with the latter. Since it is connected 
at many points with the cerebrospinal nerves, it is necessary to 
decide what shall be included in it. The logical point of separa- 
tion is that at which the cerebrospinal nerves give off branches 
which run exclusively to the sympathetic system. These 
branches of the cerebrospinal nerves form an integral part of 
this system. ‘This is well recognized in the case of.the rami com- 
’ municantes; but the principle has never been carried through 
systematically. On this basis it would include the radix brevis 
of the ciliary ganglion, the cardiac and pulmonary rami of the 
vagus, and the visceral rami of the second, third, and fourth 
sacral nerves. We pass now to a consideration of the terms 
selected from the vocabulary of the physiologists. 
The autonomic nervous system is that functional division of 
the nervous system which supplies the glands, heart, and all 
smooth muscle with their efferent innervation. It is the sum 
total of all general visceral efferent neurones both pre- and post- 
ganglionic. 
The preganglionic visceral efferent neurones have their cells 
located in the cerebrospinal axis, and their fibers make their 
exit from this axis in three streams: 1) cranial—via the III, VII, 
IX, X, XI cranial nerves; 2) thoracicolumbar—via the white 
