Lesions of the central and peripheral nervous systems produced in young rabbits by vitamin A deficiency and a high cereal intake / by Edward Mellanby.

  • Edward Mellanby
Date:
[1935?]
Catalogue details

Licence: In copyright

Credit: Lesions of the central and peripheral nervous systems produced in young rabbits by vitamin A deficiency and a high cereal intake / by Edward Mellanby. Source: Wellcome Collection.

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    deficient in vitamin A and carotene often had comparatively few degenerated fibres in the thoracic cord [l (c)]. Cervical Segment VI (rabbit A) (fig. 5).—In this region the degeneration seems to have reached its maximum in the cerebellar and ventral column tracts, while the dorsal columns appear to contain fewer degenerated fibres than in the thoracic levels. Cervical Segment II (rabbit A) (fig. 6).—The main change usually seen in this region is the scattered appearance of the degeneration in contrast to that in the lower levels of the cord; this is partly because the ascending tracts are separating out in preparation for redistribution in the brain-stem. At this level the degeneration in rabbit A is more evenly distributed between the lateral and mesial parts of the dorsal columns than is generally seen. Medulla, pyramidal decussation (rabbit A) (fig. 7).—At the level of the motor decussation many degenerating fibres are seen in the dorsal columns near the nuclei cuneatus and gracilis, and also in the dorsal and ventral spino-cerebellar and lateral spino-reticulo-thalamic tracts. Bather less degeneration is seen in the white matter which includes the ventral spino-reticulo-thalamic, spino¬ tectal and spino-olivary tracts. The fibres of the ventral columns naturally assume a more lateral position owing to the decussation of the pyramids, none of the fibres of which are affected, although some transversely cut fibres between the decus¬ sating ones are degenerated. These probably belong to the dorsal longitudinal bundle; there is some degeneration in what appear to be the vestibulo-spinal and the rubro-spinal tracts. For the sake of clarity reference will first be made to some of the higher levels of rabbit A, then a few sections of rabbit B will be described. Medulla, higher part of sensory decussation (rabbit A) (fig. 8). The inferior olivary and lateral reticular nuclei are just appearing at this level. Degener¬ ated fibres are present in the remains of the dorsal columns, although many fibres have entered the nuclei gracilis and cuneatus. The axons of some of these cells can be seen sweeping through the reticular formation as internal arcuate fibres. There is much degeneration in the dorsal and ventral spino¬ cerebellar tracts but little in the mesial fillet (cf. fig. 15). The spino-reticulo- thalamic (above the level of the pyramidal decussation the lateral and ventral spino-reticulo-thalamic appear to run together), spino-tectal and possibly also the spino-olivary tracts contain some degenerated fibres and remain in approximately the same positions as in fig. 7. Of the descending fibres the dorsal longitudinal bundle and rubro-spinal tract show some degeneration; the vestibulo-spinal, still obscured by other tracts, is probably degenerated whilst the pyramidal is unaffected. The 12th nerve containing no degenerated fibres is seen passing ventralwards through the section. Medulla, level of inferior olivary nucleus and the 4:th ventricle (rabbit A) (fig. 9).—At this level in rabbit A there is not much degeneration in the fillet,