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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    heavy on their legs and show less spontaneous movement both in the cage and outside, and in advanced cases often refuse to move at all. It will be seen below that the lesions of the central and peripheral nervous systems are often very extensive, and no doubt a closer examina¬ tion, especially tests on the sensory side, would reveal many other func¬ tional defects. A casual examination, however, makes it clear that the co-ordinating mechanism both of the head and body generally is defec¬ tive, and in some cases it is obvious that the animals are blind and probably deaf. Histological methods for demonstrating changes in nerve fibres.—Post mortem changes due to a lapse of time between death of the animal and fixation of its tissues were avoided. In some cases it was found better to fix the tissues in situ, but large organs and those with resistant capsules were dissected out and the tissues placed in the fixative. A series of experiments on peripheral nerves was undertaken in order to compare the appearances produced by rough handling in post mortem dissection and those found in experimental animals. Nerves which were crushed with forceps, stretched or left for periods up to forty-eight hours after death of the animal gave positive Marchi reactions, but in these cases the appearances were not the same as those produced by lack of carotene or vitamin A. Needless to say, changes produced by trauma were avoided as much as possible. The tissues were usually fixed in formalin (10 per cent, tap water neutralized formol saline). Although methods have been used for observing changes in the axis cylinders, those for demonstrating degeneration of the myelin in the fatty sheaths have received most attention. These include : (1) Osmic staining by Marchi’s method (with modifications) ; (2) Nile blue and sulphurous acid (Lorrain Smith [3]) ; (3) Scharlach R. For peripheral nerves, on the advice of Sir Charles Sherrington, a method described by Ramon-y-Cajal [4] was also tested in the later experiments. Fresh nerves were stained for ten to sixteen hours in 0’5 per cent, osmic acid, washed in distilled water, treated with alcohol and glycerin, and then teased before microscopic examination. This method is only useful in the case of peripheral nerves, in which it shows up the changes very beautifully (Plate VI, figs. 5 and 6). For the staining of axis cylinders several silver methods were tried, but sufficient experience of this technique was not obtained to warrant description of the results, especially of the earlier stages of axis cylinder degeneration, in the present publication. Changes certainly