Abstract
The effects of methionine, cysteine and cystine on the regeneration of the visual purple were examined. Fresh toads were used as the test animals.
In the first series of experiments, the retinae were isolated from the dark adapted animals to which methionine, cystine or cysteine, were injected previously, and their colours were compared with these of the control animals by means of Garten's table.
In the second series of experiments, the concentration of the visual purple of the premedicated and the control animals were measured by a photoelectric spectrophotometer.
It was recognized that methionine augmented the regeneration of the visual purple, but that cysteine and cystine inhibited it.
