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

  • Mellanby, Edward, Sir, 1884-1955.
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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    demyelination changes were related to hyperplasia of the epithelium of the gum margin, especially of the part adjacent to the teeth, and the subsequent invasion of the epithelial cells by micro-organisms resulting in pyorrhoea, a disease which develops in animals eating a cereal diet deficient in vitamin A and carotene [7]. Thus it is evident that all the sensory nerves of the head so far examined in young rabbits are affected by carotene deficiency, including both auditory and vestibular branches of the 8th nerve, sensory branches of the 5th nerve to the eyes and teeth and the optic nerve. On the other hand the motor cranial nerves were normal in the experiments so far completed at a time when the sensory nerves of the head showed great demyelination changes; a few degenerated fibres, however, have been occasionally seen in the 3rd nerve (fig. 12). In view of the almost clear-cut division between the susceptibility of the sensory and motor cranial nerves, it was a matter of interest to see whether other afferent and efferent nerves behaved similarly under these dietetic conditions. Sciatic nerves which contain both efferent and afferent fibres are affected by carotene deficiency (compare figs. 5 and 6 of Plate Y). On the analogy of the cranial nerves it seemed likely that the afferent fibres would be affected and that the motor fibres would escape. This is the case in the majority of the experiments for, in the rabbits brought up on carotene-deficient diets and showing typical signs of the deficiency, the ventral roots (motor) were usually free from myelin degeneration, whereas the dorsal roots were always affected (Plate VI, figs. 1 to 4). Both roots of the animal fed on cabbage are devoid of degeneration, whereas in the animal not receiving carotene the dorsal root shows much degeneration, whilst the ventral root is normal. This is the usual result, but in animals where the dietetic defect has continued for a long time some of the ventral root fibres also may be degenerated. The affection of the dorsal roots can be clearly demonstrated by Cajal’s osmic method (Plate YI, figs. 5 and 6). When the rabbit had the basal diet only, the degenerative changes are obvious (fig. 5), but when a few drops of concentrated vitamin A oil (O’l c.c. = 100 blue values), were added to the diet the fibres are normal (fig. 6). Reference has been made above to the vagus nerve. It might be expected that, although the motor fibres in this nerve would escape, its afferent fibres would suffer in the same way as most of the other afferent nerves. This has not been found to be true ; in spite of many examinations of these nerves, even in severely affected animals, no degenerative changes have so far been seen in them. In rats brought up on a vitamin A deficient diet, Zimmerman [8] found some degeneration in the vagus nerves in only four out of eight animals examined, but in all there was extensive degeneration of the medullary sheaths of the brachial plexuses and sciatic nerves. There is still a wide field left for future observation as regards these nerve changes. It is known that both the skin and epithelial surfaces are particularly susceptible to infection in vitamin A deficiency, and epithelial surfaces also