31.  Effects of Alcohol and Tobacco on the Special Senses.—­All the special senses—­hearing, seeing, smelling, tasting, feeling—­depend upon the brain and nerves.  Whatever does harm to the brain and nerves must injure the special senses also.  We have learned how alcohol and tobacco, and all other narcotics and stimulants, injure and sometimes destroy the brain cells and their nerve branches, and so we can understand that a person who uses these poisonous substances will, by so doing, injure the delicate organs with which he hears, sees, smells, etc.

32. Persons who use tobacco and strong drink sometimes become blind, because these poisons injure the nerves of sight.  The ears are frequently injured by the use of tobacco.  Smoking cigarettes and snuff-taking destroy the sense of smell.  The poison of the tobacco paralyzes the nerves of taste so that they cannot detect flavors.  Tea-tasters and other persons who need to have a delicate sense of taste do not use either alcohol or tobacco.

SUMMARY.

1.  We have five special senses—­hearing, seeing, smelling, tasting, and feeling.

2.  The ear is the organ of hearing, and has three parts, called the external ear, the middle ear, and the inner ear.  The inner ear contains the nerve of hearing.

3.  The middle ear is separated from the external ear by the drum-head.  The drum-head is connected with the inner ear by a chain of bones.

4.  Sounds cause the drum-head to vibrate.  The ear-bones convey the vibration from the drum-head to the nerve of hearing.

5.  To keep the ear healthy we must avoid meddling with it or putting things into it.

6.  The eye is the organ of sight.  The chief parts of the eye are the eyeball, the socket, and the eyelids.

7.  In the eyeball are the pupil, the lens, and the nerve of sight.

8.  The eyeball is moved in various directions by six small muscles.

9.  The eye is moistened by tears from the tear-gland.

10.  When we look at an object the lens of the eye makes a picture on the nerve of sight, at the back part of the eyeball.

11.  To keep the eyes healthy we should be careful not to tax them long at a time with fine work, or to use them in a poor light.

12.  The nerves of smell are placed in the upper part of the inside of the nose.

13.  “Colds” often destroy the sense of smell.

14.  The nerves of taste are placed in the tongue and palate.

15.  Many things which we think we taste we really do not taste, but smell or feel.

16.  Objects which have a pleasant taste are usually healthful, while those which have a bad taste are usually harmful.

17.  Pepper, mustard, etc., as well as alcohol and tobacco, have an unpleasant taste, and are not healthful.  If we use them we shall injure the nerves of taste as well as other parts of the body.