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EIGHT FIGURESThe beryllium ion has been shown by Needham ('41) and Thornton ('49, '50, '51) to be harmful to regeneration of the extremities and the tail of amphibian larvae. Following brief immersion in N/7 beryllium nitrate, the tail of the tadpole failed to regrow (Needham). After similar treatment, the amputated limb of the larval salamander not only failed to regenerate but the stump was partly resorbed (Thornton). We have studied the influence of beryllium on forelimb regeneration in the adult newt after infusion of precise quantities of the poison directly into the early growth. Regeneration ceased and, in addition, a progressive distal proximal resorption occurred, a fate which the stump of the adult limb, in contrast to the larval one, ordinarily does not suffer when the growth is blocked by other harmful agents such as x-rays, colchicine and denervation. Because of the wcl-known importance of the nerve in regeneration, histological studies, as in previous studies from our laboratory on the colchicine effect (Singer, Flinker and Sidman, '56)' were directed primarily to the possible role and fate of the nerve in the regression. No causal relation between the nerve condition and tissue destruction was revealed. However, the studies did uncover an important response and apparent participation of the epidermis in the destructive processes not described heretofore.

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