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In a gcncnil way the- cvc is considercfl by tlu- large 

 majority of persons as bein*; the ortjjan of vision, whereas, 

 in truth, it is only one of the organ> eoncerned in bringing 

 about the sensation of sight. The eye may be anatomically 

 in a perfectly healthy condition, and the images of objects 

 niav be formed with the greatest clearness and distinctness 

 on thr ntina. and. yet, the power of seeing be wanting. 

 TIk image formed on the retina produces only an imprca- 

 sioii, and this must be converted into a sensation before the 

 act of vision is accomplished. This conversion takes place 

 in the brain. That there is a certain portion of the brain 

 which presides over the function of vision, and turns all 

 the impression sent to it from the retina through the oi)tic 

 nerve into sensations, seems (f early demonstrated by numer- 

 ous experiments on the lower animals. The eye. therefore, 

 is only one of the instruments of vision. 



Let us HOW i)roceed to inquire what it is we learn by the 

 act of seeing — what knowledge of the external world is 

 brought to the mind through the medium of the eye. We 

 learn, tirst, the j)Osition of objects in space; their distance 

 from us and eacli other ; their form, size, and color. 



It may be premised that very little of our knowledge ob- 

 tained by the .sense of vision is furnished alone by the 

 images formed on the retina. In the development of the 

 intellect the .scn.ses of sight ami touch go hand in hand. 

 In fact some recent speculations seem to point to the fact 

 that sight is ordy a highW developed sense of touch. Be 

 that as it may, this important fact is clearly established, 

 that the sense of sight is an educated sense. It is not in- 

 born; it is not in.stinctivc, at least, in the higher forms of 

 l)eings. Every child that is born into the world must learn 

 to see for it.self. As .soon as an infant opens its i-yes an im- 

 age is formed on its retina, but that conveys to its young 

 mind no definite knowledge except, probably, as to outline. 

 Supi)Ose, for example, a rattle, with a ring at one end, and 

 a ball at the other, is held before it. The image of this ob- 

 ject is formed on the retina, but it is upside down, as are all 

 retinal images. How then is the child to learn the true re- 



