The photochemical breakdown of visual purple in solution and the reactions which ensue have been studied by a number of investigators during the past several years (e.g. : Nakashima, '29 ; Hosoya, '33 ; Chase, '36; Lythgoe, '37; Wald, '38; Lythgoe and Quilliam, '38). The review by Hecht ( '42) gives an excellent summary of the work in the field. T t is now definitely established that at least two colored intermediate products appear when solutions of frog visual purple, for example, are illuminated with white light.
It seemed of interest to us to study these reactions in absence of oxygen because of the known disturbance of the visual process under conditions of low oxygen tension. It is realized, of course, that the breakdown of visual purple represents only one step in this process.
Transmission of impulses along nerve fibers and across synapses is dependent upon oxygen and might be one site for effects of low oxygen pressure. Reactions in the brain may also be affected. RIcFarland and Evans, for example, ('39) have concluded from studies of the human dark adaptation curve, measured under conditions of reduced oxygen pressure, that the impairment of threshold which occurs is probably due to effects upon the neural elements of both the retina and the central nervous system.
Regeneration of visual purple in the retina is another phase of the visual process where oxygen might be involved. Jongbloed and Noyons ('36) reported a 20% increase in the oxygen consumption of isolated half-eyes of frogs in the dark as compared with illuminated controls and they assumed that this was due to resynthesis of visual purple. Chase and Smith ('39)' on the other hand, could find no difference between illuminated and non-illuminated frog retinas so f a r as oxygen consumption was concerned. Lindeman ('40) reported a "very slight