346 S, W. RANSON AND P. R. BILLINGSLEY 
By the same method he has shown that all these fibers end in the 
superior cervical ganglion. After painting that ganghon with a 
solution of nicotine no response can be obtained on stimulation 
of the upper thoracic nerves, showing that all the pathways 
through the ganglion are blocked. It is generally admitted 
that this blocking occurs at the synapse. The same effect can 
be obtained by the intravenous injection of nicotine. Since, 
however, large doses of nicotine given intravenously will not 
eliminate the effects of stimulating the internal carotid nerve or 
other branches of distribution from the ganglion, it is argued 
that there are no other synapses interposed between this ganglion 
and the tissues innervated. This conclusion is shown to be cor- 
rect by the results of the method of degeneration. 
That the degeneration, after section of the internal carotid branches, 
spreads to the periphery, is shown by stimulating the sclerotic before 
and after degenerative section. In the former case, there is a double 
effect—local contraction of the radial muscle leading to local enlargement 
of the pupil, and loeal contraction of the circular muscle of the iris; 
in the latter case, the radial contraction is lacking, the circular takes 
place as before. 
The results obtained from section of the sympathetic trunk 
in the neck and of the internal carotid nerve are all in accord with 
the conclusions to be deduced from the nicotine experiments. 
Our own observations are in full agreement with the concep- 
tions just presented. The trunk consists almost exclusively 
of medullated fibers, which would not be the case if it contained 
postganglionic fibers ascending from the thoracic ganglia. All, 
with the exception of a small bundle of unmyelinated fibers, 
degenerate in an ascending direction and the degeneration stops 
in the superior cervical ganglion. The internal carotid nerves 
are not affected either as to their myelinated or unmyelinated 
constituents. The conclusion that the only synapses on the 
functional pathways through the superior cervical ganglion are 
located in that ganglion is well established. We may now ask 
what is the nature of the synapses which are to be found there. 
Ts there a mechanism within the ganglion for the general diffusion 
of impulses such as occurs in the central nervous system? As a 
result of the diffusion of impulses in the brain and spinal cord the 
