OTHER METHODS OF STUDYING VISUAL PIGMENTS 



of the visual pigments was that of gunter, harding and stiles 

 (1951) on the spectral reflexion factors of the cat's tapetum. These 

 measurements which had been carried out on excised tapeta prompted 

 we ale (1952, 1953a) to study intact tapeta of decerebrate cats. 



The results obtained by brindley and willmer encouraged 

 RUSHTON (1952) to devise more sensitive arrangements for the in vivo 

 detection of visual pigments. Similarly, the success of the tapetal 



Fig. 7.5. Optical arrangement of apparatus for measuring density 



changes in the retinae of animals. 5", light source; L^, Lg, L3 and L4, 



lenses; G^ and Gg, glass plates; M, mirror; W, neutral wedge; Pj, 



rotating polaroid; P^, stationary polaroid; F, fiher; T, photocell. 



{Rushton, Campell, Hagins and Brindley, 1955) 



investigations led we ale (1953b) to the study of the whole eye and 

 hence of the changes occurring in the visual pigment layer. In the 

 last three years rushton and his colleagues in Cambridge, and 

 WE ALE in London have laid the foundations of new techniques which 

 have already yielded important results. 



APPARATUS 



A diagram of the apparatus used by rushton and his colleagues 

 for experiments with decerebrate rabbits or with excised eyes is 

 shown in Fig. 7.5. The light from S, a car headlamp bulb passed 



195 



