Neurology: NEUROANATOMY AND NEUROPHYSIOLOGY

THE authors sum up the results of their research as follows I.By comparing the histological structure of different nerves they conclude that (a) thick medullated fibres convey the sensation for touch.This does not preclude such fibres from conducting other forms of sensibility.(b) Medullated fibres of moderate thickness convey the sensation of pain.This does not indicate that the sensation for pain may not also be conducted by thin, non-medullated fibres. (c) Medullated fibres of fine calibre serve as sensory nerves in the viscera and to a certain extent for different special senses, also these fibres may subserve that form of sensibility known as 'visceral sensation.'II.For a long time it was a disputed point whether sensibility for pain passes from the intestines through anterior or posterior spinal nerve roots.The experiments described were performed on dogs in which the stomach was inflated in order to cause pain.It was ascertained that the sensation for pain was conducted by visceral fibres-the vagus nerve, sympathetic fibres running in the vagus, the periaortic plexus and the sympathetic trunk.The sensation of pain passing through visceral fibres is partly conducted through the posterior roots, partly through the anterior.The irritability of these visceral fibres to a faradic current is exclusively conducted through the posterior roots, and conduction of the sensation of pain from the stomach is invariably carried out by visceral fibres in the vagus.Other tracts may conduct the sensation arising from inflating the stomach.Since Foerster ascertained that a sympathetic sensory by-path first becomes more sensitive some time after cutting out the cerebrospinal sensory tract, it is believed that the above-mentioned secondary tracts for stomach sensations also function as sensory tracts in certain circumstances after the chief tracts have been eliminated.III.From the experiments described above, it was definitely shown that the sensation for pain arising in the stomach from extreme inflation is