Abstract
The changing status of the vitamin deficiencies in this country is well shown by recent publications1emphasizing the rarity of the fully developed, classic diseases and the frequency of the milder deficiencies. This is particularly true with regard to vitamin A deficiency. In a preliminary report, the present knowledge concerning the biochemical and physiologic aspects of vitamin A, the clinical and pathologic aspects of vitamin A deficiency, the mechanism of night blindness and methods of detecting mild degrees of deficiency were reviewed.2The present study deals chiefly with personal observations, and reference will be made to but a few pertinent papers. Complete bibliographies are available elsewhere.3 PROCEDURE The material forming the major portion of this paper was obtained from a study of the students of Boston University School of Medicine. Each student received a test on the biophotometer,5and those with very low readings were rechecked

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