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XXVI. A Quantum Theory of Vision. 

 By J. JOLY, F.R.S* 



THE Theory of Vision herein described originated in 

 views respecting the origin of the latent image which 

 formed the subject of an address to the Photographic 

 Convention of the United Kingdom in 1905 ( f Nature/ 

 vol. lxxii. p. 308). Some couple of years before the war 

 I returned to the subject and made experiments on the 

 retinas of oxen and sheep, believing that it might be 

 possible to detect electrons liberated by visible light falling 

 -on the retina or on the black pigment. The results were 

 negative. The war interrupted further experiments, but 

 more recently Mr. J. EL J. Poole, using more sensitive 

 apparatus, examined the black pigment of sheep and oxen 

 *is well as the fresh retinas of frogs in a state of dark 

 adaptation. These experiments also gave negative results. 

 Further consideration of the whole matter has convinced me 

 that such a surface emission of electrons was hardly probable 

 under the conditions attending the experiment: conditions 

 which involve the unavoidable presence of surface impurities. 

 The failure to detect liberated elections by no means in- 

 validates the theorv herein discussed. 



Dr. H. Stanley Allen, writing to 4 Nature' (Oct. 30, 1919), 

 refers to a theory of colour vision which on January 7th, 1919, 

 he communicated to the Rontgen Society. In this theory 

 he supposes " that photoelectric action takes place in the 

 rods or cones, so that we have a separation of electrons 

 resulting in electrification of the nerve-cells which set up 

 the nervous impulse to the brain. " An essentially similar 

 suggestion was made by Sir Oliver Lodge at the meeting of 

 the British Association in 1919. 



(1) I assume that the origin of luminous vision and of 

 • colour vision is to be sought in the liberation of electrons 

 under light stimulus within a photoelectric substance or 

 substances existing in the retina. The rhodopsin is such a 

 photosensitive substance. In the case of the rods (in which 

 rhodopsin is found) this substance acts as the basis of vision. 

 In the case of the cones the same substance is very probably 

 responsible. A strong argument for this view is to be 

 found in the fact that in the fovea, where only cones exist, the 

 spectral range of vision is in fair agreement with the spectral 



* Communicated by the Author. 

 Phil. Mag. S. 6. Vol. 41. No. 2±2. Feb. 1921. U 



