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.

    10/32 (page 384)
    phthalmia to degeneration of the trigeminal nerve has been previously described [Mellanby, 1934 a]. A typical experiment in which advanced degenerative changes were produced will be given first. Three puppies aged 8 weeks were given the following dietary mixture daily over a period of 42 weeks: separated milk powder 12-5 up to 30 g., oatmeal 75 up to 270 g., peanut oil 7*5 up to 15 c.c., meat deprived of visible fat 25 up to 60 g., baker’s yeast 3*75 up to 12 g., sodium chloride 1 up to 4 g., vitamin D as irradiated ergosterol 1000 i.u. The former quantity represents the amount of each constituent given at the beginning of the experiment and the latter the amount given when a maximum diet was being eaten. In addition, dog I had daily 30,000 i.u. of vitamin A. Dog II did not get any additional source of vitamin A throughout the feeding period. Dog III received no added vitamin A for the first 15 weeks, but for the last 27 weeks it had 30,000 i.u. daily. At the end of the experiment the vitamin A content, measured as Carr-Price blue values using a Lovibund tintometer, of the livers of the three dogs was as follows: Dog Carr-Price blue Approx, equivalent in values per g. liver i.u. per g. liver I (vitamin A-rich diet) II (vitamin A-deficient diet) III (curative experiment) 93 2800 Nil Nil 50 1500 Dog III will not be further discussed here, but will be referred to later in dealing with possible recovery. Fig. 1 represents a section of the cochlea and its components of dog I (vitamin A-rich diet). Fig. 2 is a corresponding photomicrograph of dog II (no vitamin A). (Only a few of the photomicrographs illustrative of the results obtained were made from dogs I and II. Other illustrations were sometimes chosen, not because they were different, but because they were technically better.) The most obvious pathological changes found in the labyrinths of young dogs brought up on these vitamin A-deficient diets are (a) nerve degeneration, more especially of the cochlear neurones, (6) new bony growth in the modiolus, (c) overgrowth of the internal periosteal layer of the capsule, i.e. the bone in proximity to the brain, (d) serous labyrin¬ thitis, (e) degenerative changes of the organ of Corti and sensory epi¬ thelium of the semicircular canals. Occasionally a small amount of bony overgrowth was seen in the basal whorl of the scala tympani. Changes in the 8th nerve (cochlear and vestibular divisions). The cochlear division (or its remains) of the 8th nerve is seen in Figs. 1 and 2.