Sight, and the Eye. 435 



his feet. But if a dozen dogs trot across, they will jar the bridge but 

 not set up in it a rhythmic vibration, because their untimed movements 

 neutralize each other. 



A ftw of the tones of the 44th octave have been under conditions 

 which allowed them to produce the rhythmic motion required for this 

 differentiation, and the result is the sense of sight. The whole of the 

 skin or outside of animals has been subjected to the many tones of heat 

 vibrations, and the many sorts of shocks from touch and pressure, until 

 it has acquired a sensitiveness or aptitude for being shocked and jarred 

 in a great many different ways. This sensitiveness is transmitted by 

 heredit} T from one generation to another, and each generation b}' its 

 habits produces temporary modifications which imitate differentiated 

 senses, to a certain degree. An infant gets an abstract sensation by 

 touching an object, but it requires repeated experience to be able to dis- 

 tinguish various sorts of touch. But we soon acquire a sense of touch 

 for glass, another for iron, another for wood, another for cloth, &c. , 

 and great refinements of the sense are attained in special directions, as 

 by the dealers in woolen fabrics in judging the qualities of the goods. 

 The sense of touch is then a very educable sense, and the skin as its 

 organ is easily subject to various modifications. Accordingly, we find 

 that all the sense organs are developed from the skin. The pituitary 

 membrane of the nose, the organ of smell, and the linings of the ear 

 sacs, the organs of hearing, are modified portions of the outside skin 

 punched in by invagination. The retina, the sensitive organ of sight, 

 is formed in the vertebrates by a portion of brain punched out, but the 

 brain is itself a derivative of the skin layer, so that the organ of sight is 

 no exception to the rule. This derivation is more readily seen in some 

 of the lower animals in which the development is shorter and more 

 direct. 



The sense of sight, then, is the result of a modification of a portion of 

 the skin by the impact of the ether waves of the 44th octave. As said 

 above, the first visible indication that a portion of the skin has under- 

 gone a special modification, is usually a pigment spot. It is not always 

 certain what sense is represented in the pigment spot in the lowest 

 animals, as an organ of hearing or of smell may begin in a similar modi- 

 fication. But it is settled in very many cases that the pigment spot is 

 an incipient eye. The effect of the light upon the place first alters the 

 secretions and induces the deposit of the pigment, and this deposit in 

 turn instantly becomes a factor in selecting the tones of vibration by 

 which the organism will be chiefly affected. For of course every sort of 

 pigment has the power to absorb certain tones of the radiant vibration, 

 and thus to sift and separate the rays, leaving those of suitable pitch free 

 to get in their influence on the organism without interference or loss. 



