512 



DARK ADAPTATION OF EYE 



mitted. I have therefore chosen those experiments which are prac- 

 tically free from this error of technique. 



The ordinates in Figs. 3 to 8 are given as the logarithms of the 

 intensity in order to present the data. They really must be inter- 

 preted, however, as the number of units of photochemical decompo- 

 sition products freshly formed by the Hght, because of the logarithmic 

 relation between the two. As such, what do they tell us about the 

 process of adaptation? 



6.0 



I 



•5 ^o 



•Ss 



I 



I 



sj 



/O £0 JO 4-0 



T/me — - f^inutes 



so 



Fig. 8. Dark adaptation experiment recorded by Nagel. The units of in 

 tensity are different from that of the previous figures. ^The results, however 

 are the same. 



We learned from Mya that the amount of freshly formed decom- 

 position products must be a definite proportion of the amount of 

 these products already present in the sense organ before they can 

 initiate a sensory effect. If we know the required amount of freshly 

 formed products, we therefore know the amount of the residual 

 products, because the ratio between the two is constant. The neces- 

 sary quantities of freshly decomposed photosensitive material are 



