412 S. W. RANSON AND P. R. BILLINGSLEY 
roots proximal to the spinal ganglion, Gaskell asserted ‘‘that no 
non-medullated nerves leave the central nervous system either 
in the posterior or in the anterior roots, any such nerves being in 
reality peripheral nerves for the supply of the spinal membranes.” 
This was the status of the question when Langley began his 
work. In 1892 he said: 
It may be regarded as shown that only medullated fibers run from 
the spinal cord to the sympathetic chain, and that the white rami con- 
tain very many medullated fibers whilst the gray rami contain very few. 
The asserted sharp distinction between white and gray rami stands, 
however, on a different footing. So far as concerns their histological 
characters the difference between them is rather one of degree than of 
kind, they both contain medullated fibers of various sizes, and non- 
medullated fibers. 
On such evidence alone it could not be confidently asserted 
that no preganglionic fibers left the cerebrospinal nervous system 
by way of the gray rami. This question could best be attacked 
by physiological methods, i.e., by stimulating the spinal nerves 
within the spinal canal. Langley (’92 a) showed that, while 
stimulation of the nerves which were associated with white rami 
gave rise to responses in smooth muscles and glands, stimulation 
of those which possessed only gray rami produced no noticeable 
effect on these structures. He concluded that the myelinated 
fibers in the gray rami were either not preganglionic efferent fibers 
or were too few to produce any perceptible effect. 
Most of Langley’s histological observations were made on 
teased nerves, and it has seemed worth while in connection with 
the general review of the entire sympathetic nervous system 
which is being made in this laboratory to check up his histolog- 
ical observations by a careful examination of the rami communi- 
cantes of all the spinal nerves in sections stained with osmic 
acid. In this paper the rami of only the cervical and thoracic 
nerves are considered. 
White rami communicantes. The course of the white rami 
within the sympathetic trunk will be taken up in connection with 
that nerve cord. Our present concern is with the character 
of the fibers. The white rami are not always pure, but are often 
accompanied by one or more fascicles of unmyelinated fibers 
