THE VISUAL PIGMENTS 



400 



450 



500 

 Wavelength 



550 



600 



Fig. 5.6. Difference spectra of the products formed by the reaction of 



various retinenci isomers with cattle opsin. AW-trans retinenci and neo- 



retinenci a yield no light-sensitive pigment ; /t^o-retinenei b yields rho- 



dopsin, and /^o-retinenci a yields /^o-rhodopsin. 



(After Hubbard and Wald, 1952) 



144 



