The Evolution of the Sciences 



action of the retinal purple, have developed a 

 chemical theory, which likens the eye to a 

 photographic apparatus; others, observing that 

 the illumination of the retina produces in the 

 optic nerve an electric current, have compared 

 the eye to the so-called actino-electric battery, 

 which only gives a current when acted on by 

 light. 



Bose has contributed to the consolidation 

 of this hypothesis by constructing a sort of 

 artificial eye, consisting of a silver cup filled 

 with water and sensitised internally by exposing 

 its concavity to bromine vapour. An electric 

 circuit, analogous to the optic nerve, connects 

 the outside of the cup with the water contained 

 in it and traverses a galvanometer. It is then 

 observed that the exposure of the sensitised 

 part to the light gives rise to electric responses 

 of a very original type which present the same 

 features as the graphical curves obtained from 

 a frog's eye. 



All these accumulated facts justify the 

 following conclusion. The attempts in the 

 direction of synthetic morphology, which have 



been repeatedly made during the last few years, 



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