THE SPECIAL SENSES 285 



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 exter- 

 nal nature. Primarily, this sense furnishes us with informa- 

 tion concerning the different shades of color and the different 

 degrees of brightness : these are the simple sensations of sight, 

 such as the yellowness and glitter of a gold coin. In addition 

 to these, there are composite visual sensations, produced by the 

 joint action of the other senses and by the use of the memory 

 and judgment ; such as, in 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 is valuable 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 hear- 

 ing does not yield in importance to that of sight ; and they cite 



"In conformity with this fleeting character of odorous bodies, it is a 

 law in reference to ourselves, to which, as far as I know, there is no 

 exception, that there is not any substance having a powerful smell of 

 which it is safe to take much internally. The most familiar poisonous 

 vegetables, such as the poppy, hemlock, henbane, monk's-hood, and the 

 plants containing prussic acid, have all a strong and peculiar smell. 

 Nitric, muriatic, acetic, and other corrosive acids, have characteristic 

 potent odors, and all are poisons. Even bodies with agreeable odors, 

 like oil of roses, or cinnamon, or lavender, are wholesome only in very 

 small quantities, and, when the odor is repulsive, only ic the smallest 

 quantities. So far as health is concerned, the nostril iaould be but 

 sparingly gratified with pleasing odors or distressed by ungrateful ones. 

 No greater mistake can be made in sick-rooms than dealing largely in 

 aromatic vinegar, eau de cologne, lavender water, and other perfumes. 

 This hiding of one odor by another is like trying to put away the taste of 

 bitter aloes by that of Epsom salts. Physical comfort is best secured by 

 rarely permitting an infraction of the rule that the condition of health is 

 no odor at all." Wilson on the Five Gateways of Knowledge. 



45. What is sight? What information does it furnish ? Composite visual sensation* I 

 4& Comparison between sight and hearing ? Relative capacity of deaf and blind ? 



