Experimental thiamin deficiency as a cause of degeneration in the visual pathway of the rat

THAT the fundamental alteration in the visual pathway in thiamin deficiency might be biochemical and not cellular is an opinion that has been freely expressed; yet, as there is little doubt that such a deficiency leads to a wide-spread degeneration of the central vestibular neurones (Swank and Prados, 1942), it seems reasonable enough to expect that the visual neurones might be similarly affected. It is surprising, in view of the possible relationship between thiamin and nutritional amblyopia, to discover how little experimental work on the subject has been performed. Most of the pioneers in this field were, of course, under the impression that thiamin filled the role earlier assigned to the hypothetical anti-beriberi vitamin. They believed wrongly that they were inducing only a thiamin deficiency by feeding birds with polished rice. Optic nerve degeneration in experiments of this nature is described by Barletta (1932) and Marchesini and Papagno (1935). Involvement of the visual pathway in animals on a diet deficient only i