226 STUDIES IN ELECTRO-PHYSIOLOGY: 



From the two previous diagrams it will be seen that, 

 as in Szczepanik's apparatus, the rays of light are broken up 

 and deflected at various angles before they reach the 

 pigmented cells or the rods and cones, and I assume that* 

 having arrived at, as it were, a terminal, they are, at that 

 terminal, transformed into waves of neuro-electricity, 

 which, picked up by the rods and cones, are conveyed in 

 that form to the brain. 



If something of that kind does not occur we are con- 

 fronted with another very extraordinary coincidence. 



In the Science of Light, by Percy Phillips, D.Sc., it is said : 

 " If we suppose that the sensation of light is due somehow 

 to the vibrations of electrons in the retina, the retina itself 

 will do instead of a prism for drawing out a pulse into 

 waves, and so we may have interference even without the 

 prism. We see, therefore, that it is just as simple to 

 imagine that the regular trains of waves are produced by 

 the receiver as by the transmitter of the wave. We only 

 need assume regularity of period in one or other of them.'* 



The theory that the sensation of sight is due to the 

 direct action of the vibrations of electrons in the retina 

 calls for examination. It has not been finally and con- 

 clusively proved that light consists of short electro-magnetic 

 waves. The strongest argument in its favour is Maxwell's 

 calculation that the speed of electro-magnetic waves agrees 

 with that of light, i.e., 300,000,000 metres per second. 

 That is equivalent to a velocity of 12,000,000,000 in. per 

 second, and taking the distance between the lens of the eye 

 and the receptive organ or organs of the brain to be, say, 

 6 in., impulses would, according to that theory, be trans- 

 mitted in 23^ millionth of a second. 



Moreover, these electro-magnetic waves would impinge 

 directly upon the layer of optic nerve-fibres, thence upon 

 the optic nerve-cells, and exert their electronic vibratory 

 influence upon five other layers of the retina before reaching 



