Xerophthalmia, trigeminal degeneration and vitamin A deficiency / E. Mellanby.

  • Mellanby, Edward, Sir, 1884-1955.
Date:
[1934?]
Catalogue details

Licence: In copyright

Credit: Xerophthalmia, trigeminal degeneration and vitamin A deficiency / E. Mellanby. Source: Wellcome Collection.

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    secretion comes from the Harderian gland, in primates the function is taken over by unicellular mucous glands in the retrotarsal folds and ocular conjunctiva. In vitamin A-deficient animals he found that the Harderian gland soon became atrophied and ceased to function. With the nature of these mechanisms I am not concerned in the present paper. My object is primarily to show that xerophthalmia is usually accompanied by obvious derangement of the sensory neuro¬ mechanism of the eye and that the changes in the cornea and its sensory nerve supply are related. Experimental methods. A difficulty in work of this nature, especially in the case of rabbits, is to find a diet which is compatible with good health apart from the production of the specific lesions required. Anybody with experience of animal feeding knows that a small deviation from the standard condition described may result in a high mortality and make the work useless. Eabbits, dogs, rats and chickens have been used in this research. Eabbits are for many reasons convenient for general purposes. In my experience, their eyes show xerophthalmia regularly on a vitamin A-deficient diet as given in these experiments. A standard basal diet deficient in vitamin A and carotene, which will produce the lesions described below and keep rabbits in fair general health from the age of about 9 weeks, is as follows:—oats 4 parts, bran 1 part, CaC03 1*5 per cent. 10 grms. of alfalfa heated for 36 hours at 120° C. to destroy the carotene are also given daily. The alfalfa is distributed in thin layers on the trays of an electric oven and turned frequently to allow full exposure to the air. As the rabbit grows, the oats-bran portion of the diet is gradually increased from 40 to 70 grms., but the alfalfa is not necessarily raised correspondingly. When sufficient unheated alfalfa is given instead of heated, neither xerophthalmia nor nerve degenerative changes develop, for as shown previously, carotene acts like vitamin A in preventing such degenera¬ tion (Mellanby 1931). Experimental observations. A series of rabbits brought up from the age of 8 to 10 weeks on diets deficient in vitamin A or carotene were killed at various periods after the development of xerophthalmia. Sections of the first division of the trigeminal nerve, taken peripherally and sometimes also centrally to the Gasserian ganglion, were found to contain degenerated fibres or fibres undergoing degenerative changes according to the severity of the condition. The most prominent change was in the myelin sheath and so a modification of Marches method for degenerating myelin was used as