THE VISUAL PIGMENTS 



= 0-86 while dartn all's had Amax = 530 m/^ and i)min/^max ^ 

 0-58. From Fig. 2.6, i)min/^max ratios of 0-86 and 0-58 correspond 

 to Amax displacements of 10 and 3 m^ indicating the closely-agreeing 

 values of 535 and 533 m/u respectively, for the Amax of the pike 



T 



02 



I I I I I I I I I I I I I I I I I I I I I I I I I I I I I 



-20 -15 -10 -5 +5 



Displacement from visual pigment maximum in m^ 



JL_L 



500 



505 



510 



515 



525 



530 



535 



520 

 X„.. m m/i 



Fig. 2.6. Relation between the 'purity' of retinal extracts (DminlDm&x 

 ratios) and the Amax illustrated with reference to the carp. O, Cresci- 

 telli and Dartnall's data; +, Saito's data; x , Wald's data; I, Collins 

 and Morton's limits. Note that the Amax of difference spectra (#) are 

 independent of the presence of impurities. 

 (Crescitelli and Dartnall, 1954) 



pigment. These, and some further examples, are shown in the 

 table opposite. 



The five visual pigment extracts (white perch, calico bass, blue gill, 

 carp and pickerel — see Fig. 2.4) which led wald (1939) to charac- 

 terize the pigment 'porphyropsin' had i)min/^max ratios ranging 

 from 0-51 to 0-77. The pickerel extract, for example, with Amax = 

 525 mjLL had Dmin/i^max = 0-77. Adding 7 m^, the displacement 

 correction appropriate to this ratio (Fig. 2.6) we obtain 532 m^ as 

 the Amax for the pickerel pigment. On the other hand wald's carp 

 data, after similar correction (see table), yield a Amax of 524 mju, in 

 good agreement with crescitelli and dartnall's (1954) results 

 for this fish (visual pigment 523). 



40 



