Structure and functions of the brain and spinal cord.

  • Horsley, Victor.
Date:
1892
Catalogue details

Licence: Public Domain Mark

Credit: Structure and functions of the brain and spinal cord. 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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    the meaning of the sheath or its utihty we know nothing, but it is supposed to act as an insulator. I shall now speak of the destination of nerve fibres. You have seen sufficient to know that, whatever be the structure of the nerve fibre, it either conveys an impression to the central nervous apparatus or away from it; in other w^ords, it is, as in the first case, a sensory fibre, or, as we ought more correctly to call it, an afferent channel, whereas in the second case it is a motor fibre, or an efferent channel. Taking the first set of fibres, the afferent channels, we find, of course, that we thereby include all the nerves which convey special sensations—the optic nerve or the nerve of sight, the auditory nerve, and so on— not to mention the innumerable ones which run from the vast multitude of tactile sense organs that are scattered over the skin. I cannot detail to you the structure of all these, nor is it necessary, since they are to be found described at length in every text-book of anatomy; ^ but it is incum- bent on me to give you an idea of sensory nerve- endings and the general principle on which they are all constructed in vertebrate anunals. Viewed in its simplest condition, a nerve fibre which is capable of receiving a sensory impression terminates in a little bulbous expansion (Fig. 21, f), and this bulbous * Consult especially Qnain's Anatomy.