The experimental induction of vitamin A deficiency in humans.

This is an historical account of experiments that were undertaken to determine the daily amount of vitamin A or carotene (or both) required for health of humans, by deliberately (and in one case accidentally) causing them to become vitamin A deficient. The recommended daily allowance determined by all of the experiments described arrived at roughly the same range, although large differences were reported for the time of appearance and the severity of observed signs and symptoms of the deficiency.