Nutrition in relation to bone growth and the nervous system / by Sir Edward Mellanby.

  • Mellanby, Edward, Sir, 1884-1955.
Date:
[1944?]
Catalogue details

Licence: In copyright

Credit: Nutrition in relation to bone growth and the nervous system / by Sir Edward Mellanby. Source: Wellcome Collection.

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    in a curious way as if it did not know its position in relation to the rest of the body: sometimes the head is moved up and down and sometimes from side to side, and when at rest is often askew. Two other points about the development of incoordination must be mentioned. The first is that young animals are much more quickly and intensely affected by vitamin A deficiency than older animals. Whereas incoordination develops in 2-5 months when the diet begins at 6-8 weeks of age, it may only appear after 8-12 months in dogs beginning the defective diet at the age of 4-6 months. In adult animals, say 2\ years old, the development of incoordination may only appear after 15 months or more of the defective diet, and then it is never so severe as in young animals. The second point of interest is that, if potato replaces the cereal (bread or oatmeal) in the vitamin A-deficient diets, then in my experience it is difficult to produce incoordination to more than a slight degree. It is true that potato contains a trace of carotene, but so also do bread of 85 % extracted flour and oatmeal. It looks as if potato either contains some protective substance other than vitamin A or carotene which acts like vitamin A, or it does not make the same call on vitamin A reserves as is made by bread. It may be added that, even when the livers of puppies receiving potato are found after death to be devoid of vitamin A, the animals are remarkably free from the incoordination that develops in those eating cereals. Amount of vitamin A necessary to prevent abnormality Before continuing the story of the investigation, it might be well to give some idea of the quantities of vitamin A which can prevent the abnormal changes in puppies. 100 i.u. of vitamin A per day are too small a dose to prevent all the incoordina¬ tion changes. 1000 i.u. give complete protection. Let it be assumed that 500 i.u. would be sufficient. Now 5 i.u. of vitamin A weigh 1 y, so that 500 i.u. weigh 100 y = yq mg. The average daily intake of food of an experimental puppy weighs, when dry, about 150 g. Thus one part of vitamin A in about \\ million parts of food is sufficient to prevent all defect. It will be realized from these figures how very powerful is this substance in directing proper development and function of young animals. The investigation Lesions of the peripheral and central nervous system in vitamin A -deficient animals (a) Peripheral nerves It was not unnatural that attention should be first directed to examination of the nervous system of these animals, and, in view of the general incoordination and especially of the head movement, that the vestibular division of the 8th nerve was an early objective. Examination by Marchi’s method and later by other methods soon revealed the degenerated condition of many of the nerve fibres in