The Senses 207 



The Sense of Sight 



Birds, so wonderful and interesting in all their structure 

 and life, have that most treasured of all the senses — 

 sight — so highly developed that there is nothing with 

 which we can compare it among living creatures. With 

 our great telescopes we can see to a greater distance than 

 any bird; with the high-power lenses of our microscopes 

 we can distinguish infinitely smaller objects than any 

 feathered creature is capable of perceiving, but where 

 else on the earth is there an organ of vision which in a 

 fraction of time can change itself from telescope to micro- 

 scope; where is the eye that, seeing with wonderful clear- 

 ness in the atmosphere, suddenh' adapts itself to the re- 

 fraction of water, or (less slowly, although no less surely) 

 to the darkness of night? 



Next to our powers of reasoning, we value sight above 

 all things, and fortunate indeed should we be could we 

 but exchange our imperfect vision for sight like that of 

 an eagle! Little need of spectacles or binoculars has he, 

 for the perfection of his eye enables him to become near- 

 sighted or far-sighted at will. 



''The eye," says Professor Coues, ''is an exquisitely 

 perfect optical instrument, like an automatic camera 

 which adjusts its own focus, photographs a picture upon 

 its sensitized retinal plate, and telegraphs the molecu- 

 lar movements of the nervous sheet to the optic 'twins' 

 of the brain, where the result is translated from the phys- 

 ical terms of motion in matter to the mental terms of 

 consciousness. But no part of the nervous tract, from 



