The involuntary nervous system / by Walter Holbrook Gaskell.

  • W. H. Gaskell
Date:
1920
Catalogue details

Licence: In copyright

Credit: The involuntary nervous system / by Walter Holbrook Gaskell. Source: Wellcome Collection.

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    on the same plan as the voluntary nervous system, with receptor, connector, and excitor elements. The marked difference is that the excitor elements have left the central nervous system and become peripheral, forming the various ganglia found throughout the body; while the receptor elen^nts have remained in the same position as those of the voluntary system, namely in the posterior root ganglia, and con¬ nect by means of sensory root fibres with the cells of the connector elements, which have remained in the central nervous system ; the connector fibres have passed out to reach their respective peripherally situated excitor elements. This outflow of con¬ nector fibres does not occur, at all events in the higher vertebrates, in every segment, but is interrupted at the places where the nerve plexuses for the upper and lower limbs come in ; so that we can speak of three outflows of these fibres, a bulbar, a thoracico- lumbar, and a sacral. Of these the thoracico-lumbar outflow of connector nerves connect with all the excitor neurons of the so-called sympathetic system, the sacral outflow connects with another set of excitor neurons forming the pelvic ganglionic group, and the bulbar outflow connects with the excitor neu¬ rons found in the course of the various mesomatic segmental nerves. In addition to these three main groups of connector nerves a fourth group exists confined to the region of the mid-brain, which connects with the excitor neurons forming the ciliary ganglion. These connector fibres of the involuntary system leave the cord in the spinal region by the anterior roots, so that strictly speaking the anterior root is made up not of motor fibres, but of motor fibres to the voluntary system and connector fibres to the involuntary system ; therefore as we do not think of speaking of the fibres of the pyramidal tract as motor fibres of the voluntary muscles, or as pre-ganglionic fibres, so also we ought not to speak of the corresponding fibres of the involuntary system as motor or pre-ganglionic but as connector fibres. When I speak of the motor neurons of the involuntary nervous system as having travelled out from the central nervous system in separate outflows, I do not in the least intend to imply that in my opinion they have wandered out to their destination in the shape of free cells, but simply that their ultimate position has
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