ANALYSIS OF THE SYMPATHETIC TRUNK 447 
The gray rami of the tenth, eleventh, twelfth, and thirteenth 
thoracic nerves were normal, containing the usual small number 
of fine myelinated fibers, except that in the tenth there were four 
or five fine fibers which did not appear normal. The white rami of 
these nerves were in large part degenerated, although scattered 
through each there were a considerable number of myelinated 
fibers of all sizes. The proportion of large and small fibers did 
not seem to be constant. These undegenerated fibers might, so 
far as the data given by this experiment is concerned, have had 
their cells of origin in the spinal ganglia or in the ganglia of the 
sympathetic trunk. Other experiments will show that the cells 
were located in the spinal ganglia. 
The part of the trunk including the tenth thoracic ganglion 
and internodal segment was fixed in osmic acid and cut into serial 
sections. Just below the tenth ganglion all the fibers in the 
trunk were degenerated. Many of the larger myelinated fibers 
were still seen in process of degeneration. <A little lower down a 
very small branch was seen entering the trunk, probably an 
accessory white ramus from the tenth nerve, which contained 
eleven myelinated fibers chiefly of medium size. These could 
be followed down in the trunk as a small compact fascicle for 
some distance, but became lost just above the point where the 
tenth white ramus entered the trunk, at which point the serial 
sections were imperfect, but it probably joined with the fibers 
from this ramus as it was not recognizable as a separate fascicle 
below the point where this ramus entered. Below the point of 
entrance of the tenth white ramus there was a well-defined 
fascicle of about the size of the ramus, composed of myelinated 
fibers of all sizes rather widely separated from each other. This 
fascicle from which the bulk of the fine myelinated fibers had 
disappeared could be followed downward at the surface of the 
trunk throughout the series of sections which did not include the 
entrance of the eleventh ramus. 
The twelfth thoracic ganglion and adjacent portions of the 
trunk were prepared by the pyridine silver technique. Most of 
the fibers in the trunk were degenerated, but the crescent could 
be recognized and contained a great many normal fibers, the 
