NUMBER OF PRE- AND POSTGANGLIONIC NEURONES 363 
and one-half will be so cut as to be recognizable in one section 
only. For example, if there actually were four hundred nucleoli 
in a ganglion, 774 per cent of these, or 310, would lie wholly 
in the sections and be correctly counted. Of the remaining 
90 nucleoli which are cut, 45 will be counted twice, and 45 will 
be counted once, so that the total number of nucleoli will seem 
to be 445. This source of error, amounting to approximately 
10 per cent of the number obtained by enumeration, was not 
taken into account in the enumerations made by Ranson (’06) 
and others on the cells of the spinal ganglia. It seems prob- 
able to us that the results of earlier enumerations are therefore 
somewhat too high. 
RESULTS 
The total number of fibers in the sympathetic trunk just below 
the ganglion was 3851. In the 138 sections of the ganglion which 
were searched for nucleoli 34,334 of them were found. Since 
this was done in every fourth section the total for all the sections 
would be approximately 137,336. As already stated, we believe 
that some nucleoli were cut in such a way as to be recognizable 
in two succeeding sections, and for this error a correction of 10 
per cent must be made. This would give us 123,603 as the 
number of cells actually present in the ganglion. 
In this particular specimen, then, there were 3851 myelinated 
preganglionic fibers entering the superior cervical ganglion 
which contained approximately 123,603 cells. The ratio of 
fibers to cells was approximately 1 to 32. 
DISCUSSION 
Does this ratio of 1 to 32 represent the proportion of pre- 
ganglionic to postganglionic neurones? This question raises 
two others: Are all the neurones in the ganglion postganglionic, 
i.e., cells with axons which run from the ganglion to the tissue 
innervated, and to what extent have the preganglionic fibers 
given off collaterals to postganglionic neurones in ganglia located 
farther caudalward in the truncus sympathicus? The first ques- 
tion has been discussed in detail on pages 345-354 of this issue. 
