Skeletal changes affecting the nervous system produced in young dogs by diets deficient in vitamin A / by Edward Mellanby.

  • Edward Mellanby
Date:
[1941?]
Catalogue details

Licence: In copyright

Credit: Skeletal changes affecting the nervous system produced in young dogs by diets deficient in vitamin A / by Edward Mellanby. Source: Wellcome Collection.

    6/24 page 470
    Preparation of tissues for examination At the end of each experiment, the tissues were prepared for histo¬ logical examination. In order to reduce shrinkage of soft tissues to a minimum, an intra-arterial fixation method was used and in most cases serial sections of the bones were made. The methods of preparation used were largely in accordance with Wittmaack’s technique and his solution was generally used for intra-arterial fixation. III. Bone overgrowth and its effects on the nervous system A. Skull, brain and cranial nerves A comparison of mesial sagittal surfaces of the skulls of two litter mates, one of which had a diet containing much vitamin A and the other a diet deficient in the vitamin, shows some of the regions which are especially subject to bone overgrowth. Diagrams of the cut surfaces are given in Text-figs, la and 1 b; Text-fig. la represents the mesial sagittal section of the skull and brain of a dog brought up on a diet containing much vitamin A (+ A dog), Text-fig. 1 b of a dog whose diet was otherwise the same except that it was deficient in this vitamin ( — A dog). (For the sake of brevity the terms + A and — A dog (or animal) will be used to denote dogs brought up on diets containing, or deficient in, vitamin A respectively.) It will be noted that the brain of the animal maintained on a diet deficient in vitamin A is more tightly packed into the cranial cavity than that of its litter mate receiving vitamin A. It will also be seen that the bones showing the most overgrowth are those surrounding the cerebellum, medulla oblongata and pons. In particular, all parts of the occipital bone, both above and below the foramen magnum, are greatly enlarged (Text- fig. 16) as compared with the normal (Text-fig. la). Passing forward from the supra-occipital bone, the parietal bone is also much thickened in its posterior part, but this thickening becomes less as it approaches the frontal bone. Similarly, at the base of the skull, passing forward from the hypertrophied basi-occipital bone, the enlargement of the basal portion of the sphenoid, although definite, is not so great as in the occipital bone. The effect of this overgrowth of bone at the posterior end of the skull is to press on the cerebellum and medulla oblongata and alter their shape. The cerebellum is flattened on its dorsal surface and its posterior surface is indented with the thickened occipital bone just above the foramen magnum. In the particular skull illustrated in Text-fig. 16, the tentorium cerebelli has become calcified and a wedge of bone separates
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