THORACIC TRUNCUS SYMPATHICUS 415 
posterior root ganglia.’’ It is clear from the context that he 
believed the spinal ganglia contained autonomic cells and that 
the unmyelinated fibers running from these ganglia by way of 
the white rami were of the same nature as the unmyelinated 
fibers arising from sympathetic ganglia. 
We have pyridine silver preparations of the tenth, eleventh, 
and twelfth white rami from one cat. While these are not alto- 
gether satisfactory, it is possible to see that they contain a con- 
siderable number of unmyelinated fibers. In the paper which 
follows we shall present evidence to show that these fibers arise 
in the spinal ganglia, but we believe that they are to be inter- 
preted as afferent, not as postganglionic efferent fibers. If they 
belonged to the latter category it would be hard to account for 
the negative results of stimulating the splanchnic nerves after 
injection of nicotin (p. 436). 
There has been some difference of opinion concerning the rami 
of the first thoracic nerve. Gaskell (’86) found only a gray ramus 
connected with this nerve in the dog. Edgeworth (’92) found 
that this ramus in the dog contained unmyelinated, large myelin- 
ated, and a few fine myelinated fibers. From this account we 
would conclude that there was no clear separation of the fibers 
into fascicles representing gray and white rami. Langley (’92 a) 
studied the rami of the first thoracie nerve in the cat, dog, and 
rabbit, and in every case found the highest white ramus coming 
from the first thoracic nerve. In the cat we find the gray and 
white rami of the first thoracic nerve united in a mixed ramus in 
which they appear as separate fascicles. The white fascicle con- 
tains a rather large number of fibers over 6u. It is particularly 
in the number of these large fibers that the white rami differ 
from one another. In individual white rami the content of large 
fibers was found as follows: 
First thoracic white ramus, 40 fibers over 6y in diameter, one 
of which was much larger than the others and measured 13x. 
Second thoracic white ramus, 17 fibers 6u in diameter or larger. 
Of these 5 measured 134. There were also a rather large number 
of fibers from 4 to 6u in diameter. 
