The involuntary nervous system / by Walter Holbrook Gaskell.

  • Gaskell, Walter Holbrook, 1847-1914.
Date:
1920
Catalogue details

Licence: In copyright

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

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    situated in the spinal region in the posterior horns (Fig. 2, A). We must look for the corresponding cells in the cranial region in two situations corresponding respectively to the posterior horns be¬ longing to the somatic and splanchnic segmentations. The pos¬ terior horn cells of the cord are characterized by the presence of the substantia gelatinosa Rolandi close to them, and the character¬ istic of the descending sensory root of the trigeminal (Fig. 3, A) is the presence of the substantia gelatinosa Rolandi along its whole length. In this substance are found cells with which the fibres of this root continuously make connexion, called by Edinger the end nucleus of the ascending ” root. Such cells clearly corre¬ spond to a series of connector nuclei of the same kind as those belonging to the voluntary nervous system in the segments of the spinal cord, and form in my opinion the primary connector neurons of the somatic segmentation. I imagine therefore that, as far as the somatic segmentation is concerned, the primary or segmental reflexes, which must take place in each cranial segment as well as in each spinal one, are effected through these connector neurons, as represented diagrammatically in Fig. 3, A. With respect to the splanchnic segmentation (Fig. 3, B) in which the motor neurons are found in the nucleus of the facial, nucleus ambiguus and the accessory nucleus, and the sensory neurons in the ganglia on the roots of the corresponding nerves, we must look for the connector neurons in that part of the grey matter of the medulla oblongata which continues into the spinal cord as the posterior horn. The posterior horn cells belonging to the vagus segments in the medulla oblongata have become part of the mass of cells in the floor of the fourth ventricle, known as the dorsal nucleus of the vagus, and according to Edinger the sensory roots of the vagus terminate in many of these cells and in their continuation as a cell column close along the “ descending ” root of the vagus (the fasciculus solitarius). In fact this group of cells forms the connector neurons belonging to the splanchnic segmentation in exactly the same manner as the corresponding group of cells in connexion with the sensory trigeminal fibres form the connector neurons belonging to the somatic segmentation. I imagine therefore that, so far as the splanchnic segmentation is concerned, the primary or segmental reflexes, which must take place in each cranial segment as well as in each spinal one, are