418 sf w. RANSON AND P. R. BILLINGSLEY 
large myelinated fibers they contained. He suggested the pos- 
sibility that many of the larger fibers mediate some special sense 
or subserve special visceral reflexes. ‘Many of them can be traced 
to the Pacinian corpuscles (Langley, ’00). Edgeworth (’92) 
devoted special attention to the “large-fibered sensory supply 
of the thoracic and abdominal viscera” in the dog. According 
to him, 
It was found that the large medullated sympathetic fibers exist in 
the rami communicantes of the nerves from the first dorsal to the third 
lumbar inclusive; none were found in the rami aboral to this. The 
large sympathetic fibers are found scattered among the other fibers 
in the nerve bundles forming the ramus, and not grouped together or 
isolated by any septa from the other fibers. In the uppermost dorsal 
rami the large sympathetic fibers are fairly plentiful, in the upper and 
middorsal rami they are somewhat fewer in number, whilst in the lower 
dorsal rami a sudden large increase takes place, which continues as 
far as the second lumbar ramus where the outflow practically ceases. 
A few however are constantly to be found in the third lumbar ramus— 
whilst below this as stated above none are seen. 
Edgeworth included among the large fibers those measuring 
7.2 to 9u and ignored the even larger number of fibers measuring 
less than 7» but still distinctly larger than preganglionic fibers, 
so that his results are only in a general way comparable to ours. 
He states that the large fibers are as numerous in the gray as in 
the white rami. In the cat, as we shall see, they are usually not 
present in the gray rami of the cervical and thoracic regions. 
Langley (92), working with the cat, found some large fibers, 7.2 
uw or upwards, in the gray rami of the lower cervical nerves; in the 
white and in the gray ramus of the fourth lumbar nerve, and in the 
gray rami of the fifth, sixth, and seventh lumbar nerves. These 
were not numerous, but with them were a considerable number of 
fibers about 5y in diameter. 
It has been assumed that all the large myelinated fibers are 
afferent, but are all the visceral afferent fibers large? Added 
precision could be given to this question of the myelinated vis- 
ceral afferent fibers by the study of the white rami after degen- 
eration of the preganglionic fibers resulting from section of the 
corresponding spinal nerve roots proximal to the spinal ganglia. 
We have examined the white rami of the ninth, tenth, and elev- 
