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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    all the spinal nerve centres which have to do with movement, and that is the preservation of muscular tone. I alluded to this before in speaking of the nervous system in the medusre, and I showed you Avhat was meant by tonic contraction, such as was first seen in the jelly- fish by Komanes. You will remember that the polypite of Sarsia underwent relaxation if the little nerve centres in the margin of the bell were removed. So it is with the muscles of all the higher animals, they relax if they no longer receive dis- charges from the nerve centres. It is hardly necessary to say that, since we cannot have an effect with- out a cause, these constant discharges of the nerve centres disappear under ordinary circumstances if the afferent channels leadinu- to them are inter- rupted or destroyed. As Claude Bernard found, if the posterior or afferent roots were divided, all the muscles supplied by the particular centres of which the nerve roots had been cut became relaxed The same thing, of course, is produced in a very marked degree if the motor nerve to a muscle is similarly divided. We do not know the circum- stances to meet which this constant, and, therefore, important physiological fact has been developed. Its existence is certainly conducive to quick and efficient contraction of the muscles, the functional