a2 Ss. W. RANSON 
nervous system, passing through the ganglia and plexuses with- 
out interruption, to end in the viscera. There is no satisfactory 
evidence that any afferent neurones have their cell bodies lo- 
cated in the sympathetic ganglia. The function of these afferent 
fibers is to convey to the central nervous system impulses giving 
rise to vague sensations, and other impulses, which never rising 
into consciousness, give rise to visceral reflexes. 
Visceral reflex arcs. In the gastrointestinal tract there may 
be a mechanism for purely local reflexes, i.e., there are prob- 
ably refiex ares complete within the gut wall. With this excep- 
tion the evidence strongly indicates that all visceral reflex arcs 
ass through the cerebrospinal axis and involve a series of three 
neurones: 1) visceral afferent; 2) preganglionic autonomic, and 
3) postganglionic autonomic. The purely local reflexes which 
seem to occur within the gut wall after section of all the nerves 
leading to the intestine are known as the myenteric reflexes and 
must depend upon a mechanism different from that of other 
visceral reflexes. We do not know what this mechanism is, but 
it must be located in the enteric plexuses. The term enteric 
nervous system should be restricted to the elements responsible 
for the myenteric reflex. 
In the papers which follow there will be presented some of the 
evidence that has led me to take the general position in regard 
to the sympathetic nervous system outlined in the preceding 
pages. For much of the evidence, however, it will be necessary 
for the reader to refer to the papers of Langley. To this evidence 
Dr. Johnson has made an important contribution in showing 
that there are no commissural neurones in the ganglia of the 
sympathetic trunk of the frog. The papers of Dr. Billingsley 
and myself are primarily concerned with details of structure, a 
knowledge of which will be necessary for any future attempt to 
map the functional pathways of the sympathetic nervous system. 
