In a most suggestive paper " On the structure, distribution and function of the nerves which innervate the visceral and vascular systems," Gaskell ( I ) drew attention to the fact that physiological differences observed in peripheral nerves are bound up with morphological differences, so that groups of nerves of the same function can be grouped under the same morphological laws of structure and distribution. In this communication attention is drawn to the fact, that certain anterior spinal roots-namely from the 10th to the zsth-contain a relatively large number of medullated fibers varying in size from 1.8
and that these form the greater portion of all the nerve fibers found in the nerves commonly known as white, rami ; and further, that these small, medullated nerve fibers pass to the metameric sympathetic ganglia and in three main streams-upwards into the cervical sympathetic ganglia, downwards into the lumbar and sacral ganglia, and outwards into the prevertebral and terminal sympathetic ganglia. In the white rami and in the splanchnic nerves a small number of larger medullated nerve fibers were found, clearly shown in his figure (8) of a cross section of a typical white ramus as seen when stained with osmic acid. These observations corroborated in part and extended those of Bidder and Volkmann (2) who had reached the conclusion " that in the various typical nerves of to 2.7