196 THE SPECIAL SENSES. 



sense of smell a means of protection against their natural 

 enemies, of whose approach they are in this manner warned. 

 By training this sense in the dog, and making it subservi- 

 ent to his use, man is able to hunt with success certain shy 

 and very fleet animals, which otherwise he could but sel- 

 dom approach. Among men, individuals differ greatly in 

 respect to the development of this sense ; and especially 

 in certain savage tribes it is found to be extremely deli- 

 cate. Humboldt states that the natives of Peru can, by 

 this sense, distinguish in the dark between persons of dif- 

 ferent races. 



45. The Sense of Sight. Sight, or Vision, is the 

 special sense by means of which we appreciate the color, 

 form, size, distance, and other physical properties of the 

 objects of external nature. Primarily, this sense furnishes 

 us with information concerning the different shades of 

 color and the different degrees of tightness: these are 

 the simple sensations of sight, such as the yellowness and 

 glitter of a gold coin. In addition to these, there are com- 

 posite visual sensations, produced by the joint action of 

 the other senses and by the use of the memory and judg- 

 ment; such as, m the case of the coin, its roundness, 

 solidity, size, its distance and direction from us. So that- 

 many of our sensations, commonly considered as due to 

 sight, are in reality the results of intellectual processes 

 which take place instantaneously and unconsciously. 



46. This faculty not only has value in the practical 

 every-day affairs of life, but it contributes so largely to the 

 culture of the intellect and to our higher forms of pleasure, 

 that some writers are disposed to rate it as the first and 

 most valuable of the senses. Others, however, maintain 

 that the sense of hearing does not yield in importance to 

 that of sight; and they cite in support of their position 



45. What is sight? What information docs it furnish ? Composite visual sen- 

 cat ions ? 



46. Comparison between sight and hearing? Relative capacity of deaf and 

 blind? 



