On the mammalian nervous system : its functions, and their localisation determined by an electrical method / by Francis Gotch and Victor Horsley.

  • Gotch, Francis, 1853-1913.
Date:
1891
Catalogue details

Licence: Public Domain Mark

Credit: On the mammalian nervous system : its functions, and their localisation determined by an electrical method / by Francis Gotch and Victor Horsley. Source: Wellcome Collection.

Provider: This material has been provided by the Augustus C. Long Health Sciences Library at Columbia University and Columbia University Libraries/Information Services, through the Medical Heritage Library. The original may be consulted at the the Augustus C. Long Health Sciences Library at Columbia University and Columbia University.

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    that involving the activity of the corpuscles. If, then, on exciting a mixed nevve it be found that excitatory processes are present in a distant portion of the cord under investigation, these may be due to— (1.) The propagation of tliese processes from the point of stimulation along direct and continuous nerve fibres which pass into the cord and on through the investigated region ; (2.) To the reflex discharge of interposed cells in the cord, brought about by the arrival of excitatory processes which, having travelled up the nerves from the point of stimulation, have entered upon paths ending in cells. These cells being thus awakened, themselves start nerve impulses which travel on up the cord, and, reachhig the investigated area, produce the obsei-ved electrical effects ; (3.) To the mixture of effects produced by impulses both in direct paths and the indirect ones just described. It must, therefore, be.borne in mind throughout the present research that these different causes may be operating in the production of the electrical effects observed ; hence, one of our first experimental enquiries was to endeavour as far as possible to discriminate between the effects referable to the direct fibres actually excited, and those which were related but indirectly with these fibres, being primarily associated wdth channels connecting the area of investigation with corpuscular mechanisms in the cord, This we have attempted to do by employing such a low intensity of stimulation as should in any particular degree of narcosis be sufficient to evoke nerve impulses, as evidenced by electrical changes, and, at the same time, not so intense as to arouse any sign of reflex movement. The weak impulses thus generated In the excited nerve presumably pass for the most part, if not entirely, along direct nerve fibres in the cord which are not in relation with nerve cells before arriving at the region observed (mid-dorsal); the evidence to be detailed later strengthens this presumption. The subject matter now dealt with really comprises the whole question of the rela- tion of the bulbo-spinal system to the lumbar nerves. It is obvious that this relation- ship is one which may be discussed under three heads according to the particular part of the nerve tract under observation. First, the characters of the nerve impulses which pass along the channels of the coi-d after entering it by its nerve roots ; Second, the characters of the nerve impulses which, aroused by excitation of the channels of the cord and passing out into its nerve roots, descend along fibres of the mixed nerve ; Third, the characters of the nerve impulses which enter and leave the cord by virtue of its so-called central structures and their various connections. Of these three groups, the first alone will be treated of in the present chapter, the second and third being reserved for Chapters X. and XI. respectively. 3 G 2