On the Refractive Index of the Retina.

Summary. 1. As a rule the refractive index for dark adapted retinae of cows was 1.358. 2. In a material of 321 cases the light adapted retina's index was 1.3610 ± 0.0008. 3. The experiments carried out support the supposition expressed by K ühne Aand E wald that visual purple exudes water when it is bleached. For this reason the value of the refractive index in light adapted retinae is higher than that in dark adapted ones. 4. The retinal refractive index in newly born calves in a material of 104 samples was 1.3621 ± 0.0012. 5. The refractive index for the retinae of pigs was 1.35733 ± ± 0.00167. The low index value possibly depends on the fact that the retina is poor in rods. 6. The refractive index in horses' eyes was as a rule 1.361.