Abstract
specific conditions with the use of excised, perfused rabbit retinas. Retinas incubated in lowsodium media, in which sodium ions of the standard medium were replaced by lithium and choline ions, immediately lost their responsiveness to the luminous stimulus. However, the PHI component of the ERG recovered when the sodium concentration of the medium was restored to normal. The Pll component remained subnormal. The inhibitory effect of ouabain upon the ERG was not observed in low sodium media. This result was interpreted as providing supportive evidence that the mode of action ofouabain involves abolition of some of the sodiumdependent enzyme systems of retinal cells concerned with generation of the Pll and PIII components of the ERG. The responses to the second fash of a pair of fashes survived longer than those to the first.