THE CERVICAL SYMPATHETIC TRUNK 341 
of a closed network on the surface of a cell which we were in- 
clined to regard as a true pericellular plexus. From all these 
facts we conclude that the pericellular network is ordinarily not 
stained in the pyridine silver preparations, but that the axonie 
constituents of the intercellular plexuses come out with great 
clearness. 
It will be remembered that Michailow regarded the plexus 
under discussion as forming a true net by means of which all or 
at least many of the fibers are united together, one neurone 
being thus united to another. This would mean diffuse conduc- 
tion in the ganglion, which must then act as a whole. This is 
directly at variance with what is known of the physiology of the 
sympathetic ganglia. There is no evidence that diffuse con- 
duction occurs in any of them, and in at least two, the superior 
cervical and the coccygeal ganglia, Langley (00a, ’04) has been 
able to show that diffusion does not occur. We will take this 
up in connection with a discussion of the synapses in the sym- 
pathetic ganglia. 
Neither Dogiel nor Huber gives the impression that the inter- 
cellular plexus is a closed net and we have carefully examined 
pyridine silver preparations for evidence in this regard. While 
branching fibers are common, it can usually be seen that a larger 
fiber is dividing into two smaller ones. The junction of three 
fibers of the same size as at the nodal point of a net does not seem 
to occur. Often two fibers could be seen crossing, one im- 
mediately over the other, but each retained its individuality 
and sharp contour. If the plexus were a true network, one should 
be able to find closed meshes surrounded on all sides by anasta- 
mosing fibers—an arrangement which does not seem to occur. 
In the pyridine silver preparations of the human superior 
cervical ganglion the fibers of the intercellular plexus stand out 
prominently, as is seen in figure 5. The fibers of this plexus 
mingle with the branches of the long or extracapsular dendrites. 
Except that the plexus is not as uniformly distributed throughout 
the ganglion and is perhaps not quite so dense, it resembles that 
in the dog. There is, however, one important feature in which 
the human ganglion differs. Fine axons, apparently continuous 
