Abstract
Observations were made on 350 men over ten months. It was found that vitamin B_2 deficiency occurred more readily under some unusual environmental conditions, such as at low ambient temperatures (-10 to 10℃) with high humidity (85%) or in sunless atmosphere. The subjects were put on a standard meal of 2900 cal. containing 95 g of protein, 18 g of fat, 190μg of thiamine, 150μg of riboflavin, 14 mg of ascorbic acid and an ample amount of vitamin A, riboflavin only lacking entirely. A considerable reduction in the visual power and dark adaptation occurred after seven months which could completely be restored by administration of riboflavin.
