OTHER METHODS OF STUDYING VISUAL PIGMENTS 



400 



450 



600 



500 550 



Wavelength in mp 



Fig. 7.3. Evidence for a blue-sensitive pigment in the retinal extract of 

 Rana esculenta. (A) Curve 1 , density spectrum of unexposed extract ; 

 curves 2, 3 and 4, density spectra of the extract after 2, 4 and 5 hr 

 exposure, respectively, to yellow light (570 mfX) which removes most of 

 the visual purple ; curve 5, after exposure to white light. (B) Difference 

 spectra constructed from the (A) curves. The dashed curve (obtained by 

 correcting 4-5 for the contribution of residual visual purple) is the 

 density spectrum of the blue-sensitive pigment. 

 {Dartnall, unpublished) 



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