The experimental production of deafness in young animals by diet / by Edward Mellanby.

  • Edward Mellanby
Date:
[1938?]
Catalogue details

Licence: In copyright

Credit: The experimental production of deafness in young animals by diet / by Edward Mellanby. Source: Wellcome Collection.

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    and carotene [Zimmerman, 1933]. Again, the cereal content of the diet may be very high and yet, in the presence of sufficient vitamin A and carotene, little or no nerve degeneration will be produced. On the other hand, changes in the type of cereal eaten or the addition of certain cereal products may alter the degree of degeneration. The experimental diets are made up of ordinary foodstuffs, except for the irradiated ergosterol, and are rich in all substances of the vitamin B complexes. One of the afferent nerves affected by demyelination changes under these dietetic conditions is the 8th, both cochlear and vestibular divisions, the former more so than the latter. Degenerate changes in the vestibular nerves are associated with inco-ordinate movements of locomotion of the animal, as might be expected. Young dogs showing this condition are also inattentive and do not respond to the call of people at close range, a characteristic which distinguishes them from, normal puppies. This inattention is doubtless due partly to deafness. The present paper is concerned with these abnormal changes due to vitamin A deficiency, and contains a description of the pathological condition of the labyrinthine capsule, both of its nerve supply and the bone itself. When a rich source of vitamin A is added to the diet while every other condition of diet and environment is kept constant, the animals remain normal in behaviour and the labyrinthine capsule escapes pathological change. x411 young animals examined up to date, i.e. dogs, rabbits and rats, react to the above dietetic defects, so far as nerve degeneration is concerned, in the same way, differing of course in degree. The new facts, especially concerning bone hyperplasia, described in this paper, refer for the time being to the dog. There is, however, no doubt that bone hyper¬ plasia takes place in the rabbit and probably in the rat, and will be described in a future paper. Histological technique Since the degenerative changes of a nutritional nature in the 8th nerve were first seen and described, the need of following up and examining in detail the internal ear itself has been constantly in mind. Many of the animals fed over a fairly long period on diets very deficient in vitamin A were obviously deaf, and unsuccessful attempts were made to grade the degree of deafness in dogs and rabbits by observing their reactions to sound. The earlier histological preparations made for the detailed exami¬ nation of the finer structure of the cochlea and vestibule were unsatis¬ factory. Last year I discussed the subject of deafness in animals on