SACRAL SYMPATHETIC TRUNK OF CAT 95 
nodal segment caudad to the origin of the associated gray ramus. 
Fibers of this type were the only medullated fibers seen in certain 
of the experimental material. 
As to the total number of medullated fibers at various levels 
in the sacral trunk, the numbers given in the succeeding para- 
graphs are probably too low, as the oil-immersion lens was not 
used to check up on the number of the smallest fibers. The 
enumerations were carefully made under a 4-mm. objective and 
a 10X-ocular, and the results are sufficiently accurate to serve 
as a basis for comparison with the degenerated specimens. The 
figures given are all for the same normal specimen. 
In a cross-section of the seventh lumbar internodal segment 
(i.e., the segment connecting the seventh lumbar with the first 
sacral ganglion) a total of 444 medullated fibers was counted. 
Of this number there were counted seven fibers 94 in diameter, 
eighty fibers 6 to 7u, and 357 of various sizes from 1.5 to 5z. 
The fibers are evenly distributed over the entire field of the 
section without any apparent grouping as to size (fig. 2). The 
very largest fibers, however, appear to be more frequently located 
near the periphery of the trunk. 
Figure 3 shows the arrangement of the medullated fibers as 
they pass through the first sacral ganglion. There are about 
300 medullated fibers in this section, and as the trunk just above 
the ganglion contains approximately 450, it seems probable 
that the decrease in number is due to the termination in the 
ganglion of a proportionate number of preganglionic efferent 
fibers. The ramus which is seen in the process of formation in 
this section contains, a few sections caudad where it is completely 
formed and separated from the trunk, 107 medullated fibers of 
all sizes seen in the trunk. 
In the first sacral internodal segment (fig. 4) were counted 
313 medullated fibers, a decrease of 131 from the number in the 
seventh lumbar segment. This segment was represented by a 
single nerve strand, but it contained nerve cells throughout its 
entire length. 
Right and left second sacral ganglia were fused together in 
this specimen, a condition commonly seen in the sacral and 
