The effect of vitamin A deficiency on the development of the retina and on the first appearance of visual purple

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Abstract
An attempt to produce young rats with severe vitamin-A deficiency failed because depletion of the maternal rats resulted in prolonged labor with stillborn litters or high neonatal mortality. Examination of the eyes of 59 rats 3-61 days old from less severely depleted mothers, revealed no abnormalities in the development of the retina during the first 12 days of life. The first appearance of visual purple was delayed until the 21st day (normal 12-15) and even then the amt. was reduced. Development of the outer limbs of the retinal rods was retarded but never prevented entirely and in all but 2 instances showed lack of differential staining. Daily doses of cod-liver oil restored the staining reaction after 3 days but not the structural damage after 6 days. The results indicate that vitamin-A deficiency affects the formation of the visual purple directly and not through its action on the rods. They are compatible with Wald''s conception of the visual purple system.