212 THE NATURE OF ANIMALITY. 



mit the rays of objective light, which impinge upon them, in 

 given directions to the retina. In the retina, the objective 

 light, by the instrumentality of certain structural arrange- 

 ments — the rods and cones — induces the usual nerve action in 

 the fibres of the optic nerve. This nerve action, common to 

 all nerve fibres, is a polaric physical action ; proceeding by 

 the optic nerve from the retina to the nervous centre of 

 vision in the brain. At that nervous centre the consciousness 

 of the animal interprets the objective or physical nerve action 

 as subjective light. 



20. This subjective light, or light usually so termed, is a 

 mere condition or form of consciousness ; it is the psychical 

 co-ordinate of the physical luminiferous oscillations, which 

 are merely its mediate inducing cause. 



21. By these successive actions, physical and psychical, 

 co-ordinated by the optical construction of the eye-ball, and 

 of the light-perceiving portion of the brain, the animal per- 

 ceives at once the object presented to its eye. It sees it 

 directly. The animal can determine without effort not only 

 the distance of the object, but also without hesitation, the 

 precise positional relations of the object to surrounding 

 objects, and to itself. 



22. This faculty of using the organs of vision, and the 

 other organs of special sense, as immediate instruments, is 

 peculiar to the animal. Man cannot do so. To him the 

 organs of sense are mediate instruments. He must learn how 

 to make use of them. He must learn how to interpret their 

 revelations under the guidance of his rational consciousness. 

 The animal requires no such self-education. 



23. The illustration which I have given of the process of 

 vision in the animal, affords fundamental evidence of the 

 peculiar character of its conscious principle. Now, if we 

 assume, as we may safely do, that all the other conditions of 

 its consciousness are fundamentally determined in the con- 



