The Special Senses 263 



proverb that one should never rub his eyes except with 

 his elbows. 



The eyes of young infants should not be exposed to 

 electric lights or to the direct rays of the sun. Special care 

 should be taken with children's eyes during and after an 

 attack of measles and scarlet fever. 



Glasses should be worn when they are needed A failure 

 to do this usually causes much unnecessary suffering. It 

 is far from wise to postpone as long as possible the first 

 use of glasses. 



412. Effect of Alcohol 

 and Tobacco upon Vision. 



A wide comparison of cases FlG . , 38 . The Actual Size of the Test- 

 by Careful observers proves Type, which should be seen by the 

 that a large fraction of Normal Eye at a Distance of Twenty 



Feet, 

 those who indulge in 



strong drink suffer from some disease of the eye. The 

 earlier and slighter forms of injury done to the eye by the 

 use of intoxicants are quite familiar, the watery condition 

 of the eye and of the lids, and its red and bleared aspect. 

 The nerves controlling the circulation of the eye are 

 partially paralyzed, and thus the relaxed vessels become 

 distended. 



Long use of intoxicants may produce diseases of the 

 retina, involving, in many cases, marked diminution of 

 acuteness as well as quickness of vision. 



What is known to oculists as "tobacco blindness," and 

 a temporary form of color-blindness, may result from an 

 excessive use of tobacco. 



The ill effects of tobacco, and especially of cigarettes, 

 upon the eyes of the young are generally recognized. 



413. The Sense of Hearing. The structure of the human 

 ear is much more complicated than is generally supposed. 



