422 S. W. RANSON AND P. R. BILLINGSLEY 
In spite of the presence of a few myelinated sensory fibers in 
the gray rami ‘“‘no reflex of any kind has been obtained by stimu- 
lating them” (Langley, 00). This may be due to theirsmall 
number, or it may be as Langley (92 a) has intimated, to the 
fact that these large afferent fibers are not fibers of general 
sensibility. 
STRUCTURE OF THE THORACIC PORTION OF THE TRUNCUS 
SYMPATHICUS 
In order to understand the structure of the sympathetic trunk 
it is necessary to think of it as a ganglionated nerve which re- 
ceives preganglionic myelinated fibers from the various white 
rami and through which these fibers are distributed to ganglia 
more or less remote from the point where the fibers enter the 
trunk (fig. 4). Above the sixth thoracic ganglion the trunks 
consist chiefly of ascending preganglionic fibers from the upper 
white rami destined to end in the upper thoracic, stellate, and 
cervical ganglia. Below the tenth thoracic ganglion it consists 
chiefly of descending preganglionic fibers from the lower thoracic 
and lumbar white rami to the more caudal ganglia of the trunk 
and to the splanchnic nerves. From the sixth to the ninth ganglia 
it contains both ascending and descending preganglionic fibers. 
The lowest known origin of ascending fibers to the superior cervi- 
cal ganglion is from the seventh thoracic white rami and consists 
of pilomotor fibers for the face and neck. Fibers ascend to the 
stellate ganglion from white rami as low as the ninth. The 
highest fibers running to the splanchnic nerve come from the 
fifth or possibly the fourth. Fibers from a given white ramus 
may be distributed to from five to ten successive ganglia of the 
sympathetic trunk, though the branches of an individual pre- 
ganglionic nerve fiber would be distributed to a smaller number. 
These statements are based on Langley’s (92 a, ’00, 03 a) work 
on the cat. In more general terms this distribution of the 
fibers of the white rami has been known for many years and 
was well stated by Gaskell (’86). According to him, the white 
rami from the second to the fifth thoracic nerves, inclusive, in the 
dog are directed upward, below the fifth they are directed mainly 
