THE ORGANS OF SPECIAL SENSE. 473 



are but special modifications of the general sensations of 

 the body. In fact, comparative anatomy could even in 

 such a complicated structure as an eye find between the 

 highly developed human eye and the mere pigment spot in 

 the skin of some of the lowest animals many intervening 

 gradations. The little pigment spot at the tip of the ray of 

 the starfish which enables that animal to detect possibly 

 the direction of the light merely, is but a slight advance in- 

 deed from the property of general sensations possessed by 

 its entire nervous system. The localization of the pigment 

 at other points than those of the tip of the ray might suffice 

 to arouse light sensations. Such exceedingly simple forms of 

 eye, were, however, in the development of the animal forms 

 more and more expanded, specialized and complicated, un- 

 til finally, from a somewhat common sensation, there re- 

 sults the highly modified retina of the eye with its acces- 

 sories. 



THE OBJECTIFICATION OF OUR SENSATIONS. 



If it is true that special sensations are but specialized 

 general sensations, the question naturally arises why such 

 special sensations should be referred to the external world, 

 whereas the general sensations are not so referred. The 

 answer to this is at hand. It is among the simplest obser- 

 vations on children or adult defective people to show that 

 these special sensations are at first not objectified. The 

 reference of our sensations to the external world is gradual 

 and the result of our early education and experience. In 

 the case of touch, for instance, an object is brought in con- 

 tact with the skin and a sensation results. By repeated ob- 

 servation it has been found that such a sensation comes from 

 the foot, say. This the individual has found by observing 

 possibly an object lying on his foot. Removing the same, 

 he noted the cessation of the sensation. In this way he 

 finally infers when he feels this same sensation that it must 

 come from the foot. These inferences become so trust- 

 worthy finally to the individual that he does not realize at 



