BRANCHES OF GANGLION CERVICALE SUPERIUS 383 
table 8 we also found a considerable number of these larger sizes. 
Are we to regard these fibers measuring about 6.6u as very large 
postganglionic elements or as fibers of another character, for 
example, sensory, which, as a variation, have been included in 
these particular specimens? 
CONCLUSIONS 
All of the branches of the superior cervical ganglion, exclusive 
of the sympathetic trunk, contain, in addition to great numbers 
of unmyelinated fibers, also a limited number of myelinated 
fibers. Nearly all of these have a diameter of less than 4.5y, 
though in a few specimens we have found some fibers measuring 
more than 6.64. The internal carotid nerve seems to contain 
regularly a rather large number of myelinated fibers and the 
gray rami to the first three cervical nerves a smaller number. 
The same relation holds for the proportion of myelinated fibers 
per square millimeter in these nerves. Otherwise there is nothing 
characteristic about the myelinated fiber content of any of these 
branches. 
The great majority if not all of these fibers are postganglionic. 
This has been ascertained for the internal carotid nerve by 
degeneration experiments. If regularly myelinated preganglionic 
or afferent fibers were present in any of the branches we should 
expect to find evidences of them in the tabulated data given 
in this paper. The best explanation of the great variation in the 
number of myelinated fibers in different specimens of the same 
nerve is that myelination takes place in a limited number of 
postganglionic fibers and that this occurs without law or order. 
If any functional group of postganglionic fibers was more likely 
to become myelinated than another we should expect to find 
certain of the functionally diverse branches of the superior 
cervical ganglion better myelinated than others, but this is not 
the case, except for a slightly better myelination of the internal 
carotid nerve and a somewhat poorer myelination of the gray 
rami. The indications are that myelination is not related in 
any very direct way to the function of the fibers. 
