First Book In Physiology And Hygiene Part 17

~27.~ The use of the sense of taste is to give us pleasure and to tell us whether different substances are healthful or injurious. Things which are poisonous and likely to make us sick almost always have an unpleasant taste as well as an unpleasant odor. Things which have a pleasant taste are usually harmless.

~28. Bad Tastes.~--People sometimes learn to like things which have a very unpleasant taste. Pepper, mustard, pepper-sauce, and other hot sauces, alcohol, and tobacco are harmful substances of this sort. When used freely they injure the sense of taste so that it cannot detect and enjoy fine and delicate flavors. These substances, as we have elsewhere learned, also do the stomach harm and injure the nerves and other parts of the body.

~29. The Sense of Touch.~--If you put your hand upon an object you can tell whether it is hard or soft, smooth or rough, and can learn whether it is round or square, or of some other shape. You are able to do this by means of the nerves of touch, which are found in the skin in all parts of the body. If you wished to know how an object feels, would you touch it with the elbow, or the knee, or the cheek? You will say, No.

You would feel of it with the hand, and would touch it with the ends of the fingers. You can feel objects better with the ends of the fingers because there are more nerves of touch in the part of the skin covering the ends of the fingers than in most other parts of the body.

~30.~ The sense of touch is more delicate in the tip of the tongue than in any other part. This is because it is necessary to use the sense of touch in the tongue to a.s.sist the sense of taste in finding out whether things are good to eat or not. The sense of touch is also very useful to us in many other ways. We hardly know how useful it really is until we are deprived of some of our other senses, as sight or hearing. In a blind man the sense of touch often becomes surprisingly acute.

~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.

18. We feel objects by means of the sense of touch.

19. The sense of touch is most acute at the tip of the tongue and the ends of the fingers.

CHAPTER XXVI.

ALCOHOL.

~1.~ As we learned in the early part of our study of this subject, alcohol is produced by _fermentation_. It is afterwards separated from water and other substances by _distillation_. We will now learn a few more things about alcohol.

~2. Alcohol Burns.~--If alcohol is placed in a lamp, it will burn much like kerosene oil. Indeed, it does not need a lamp to help it burn as does oil. If a few drops of alcohol are placed upon a plate, it may be lighted with a match, and will burn with a pale blue flame. Thus you see that alcohol is a sort of burning fluid.

~3.~ The vapor of alcohol will burn also, and under some circ.u.mstances it will explode. On this account it is better not to try any experiments with it unless some older person is close by to direct you, so that no harm may be done. Alcohol is really a dangerous substance even though we do not take it as a drink.

~4. An Interesting Experiment.~--We have told you that all fermented drinks contain alcohol. You will remember that wine, beer, ale, and cider are fermented drinks. We know that these drinks contain alcohol because the chemist can separate the alcohol from the water and other substances, and thus learn just how much alcohol each contains.

~5.~ If we should remove all the alcohol from wine, no one would care to drink it. The same is true of beer and cider. It is very easy to remove the alcohol by the simple process of heating. This is the way the chemist separates it. The heat drives the alcohol off with the steam. If the heating is continued long enough, all the alcohol will be driven off. The Chinaman boils his wine before drinking it. Perhaps this is one reason why Chinamen are so seldom found drunken.

~6.~ By a simple experiment which your parents or your teacher can perform for you, it can be readily proven that different fermented drinks contain alcohol, and also that the alcohol may be driven off by heat. Place a basin half full of water upon the stove where it will soon boil. Put into a gla.s.s bottle enough beer or cider so that when the bottle stands up in the basin the liquid in the bottle will be at about the same height as the water in the basin. Now place in the neck of the bottle a closely fitting cork in which there has been inserted a piece of the stem of a clay pipe or a small gla.s.s tube. Place the bottle in the basin. Watch carefully until the liquid in the bottle begins to boil. Now apply a lighted match to the end of the pipe-stem or gla.s.s tube. Perhaps you will observe nothing at first, but continue placing the match to the pipe-stem, and pretty soon you will notice a little blue flame burning at the end of the stem. It will go out often, but you can light it again. This is proof that alcohol is escaping from the liquid in the bottle. After the liquid has been boiling for some time, the flame goes out, and cannot be re-lighted, because the alcohol has been all driven off.

[Ill.u.s.tration: Alcohol experiment.]

~7. The Alcohol Breath.~--You have doubtless heard that a person who is under the influence of liquor may be known by his breath. His breath smells of alcohol. This is because his lungs are trying to remove the alcohol from his blood as fast as possible, so as to prevent injury to the blood corpuscles and the tissues of the body. It is the vapor of alcohol mixed with his breath that causes the odor.

~8.~ You may have heard that sometimes men take such quant.i.ties of liquor that the breath becomes strong with the vapor of alcohol and takes fire when a light is brought near the mouth. These stories are probably not true, although it sometimes happens that persons become diseased in such a way that the breath will take fire if it comes in contact with a light. Alcohol may be a cause of this kind of disease.

~9. Making Alcohol.~--It may be that some of our young readers would like to find out for themselves that alcohol is really made by fermentation. This may be done by an easy experiment. You know that yeast will cause bread to "rise" or ferment. As we have elsewhere learned, a little alcohol is formed in the fermentation of bread, but is driven off by the heat of the oven in baking, so that we do not take any of it into our stomachs when we eat the bread. If we place a little baker's yeast in sweetened water, it will cause it to ferment and produce alcohol. To make alcohol, all we have to do is to place a little yeast and some sweetened water in a bottle and put it away in a warm place for a few hours until it has had time to ferment. You will know when fermentation has taken place by the great number of small bubbles which appear. When the liquid has fermented, you may prove that alcohol is present by means of the same experiment by which you found the alcohol in cider or wine. (See page 160.)

~10.~ Alcohol is made from the sweet juices of fruits by simply allowing them to ferment. Wine, as you know, is fermented grape juice. Cider is fermented apple juice. The strong alcoholic liquor obtained by distilling wine, cider, or any kind of fermented fruit juice, is known as brandy.

~11. How Beer is Made.~--Beer is made from grain of some sort. The grain is first moistened and kept in a warm place for a few days until it begins to sprout. The young plant needs sugar for its food; and so while the grain is sprouting, the starch in the grain is changed into sugar by a curious kind of digestion. This, as you will remember, is the way in which the saliva acts upon starch. So far no very great harm has been done, only sprouted grain, though very sweet, is not so good to eat as grain which has not sprouted. Nature intends the sugar to be used as food for the little sproutlet; but the brewer wants it for another purpose, and he stops the growth of the plant by drying the grain in a hot room.

~12.~ The next thing the brewer does is to grind the sprouted grain and soak it in water. The water dissolves out the sugar. Next he adds yeast to the sweet liquor and allows it to ferment, thus converting the sugar into alcohol. Potatoes are sometimes treated in a similar way.

~13.~ By distilling beer, a strong liquor known as whiskey is obtained.

Sometimes juniper berries are distilled with the beer. The liquor obtained is then called gin. In the West Indies, on the great sugar plantations, large quant.i.ties of liquor are made from the skimmings and cleanings of the vessels in which the sweet juice of the sugar-cane is boiled down. These refuse matters are mixed with water and fermented, then distilled. This liquor is called rum.

~14.~ Now you have learned enough about alcohol to know that it is not produced by plants in the same way that food is, but that it is the result of a sort of decay. In making alcohol, good food is destroyed and made into a substance which is not fit for food, and which produces a great amount of sickness and destroys many lives. Do you not think it a pity that such great quant.i.ties of good corn and other grains should be wasted in this way when they might be employed for a useful purpose?

~15. The Alcohol Family.~--Scientists tell us that there are several different kinds of alcohol. Naphtha is a strong-smelling liquid sometimes used by painters to thin their paint and make it dry quickly.

It does not have the same odor as alcohol, but it looks and acts very much like it. It will burn as alcohol does. It kills animals and plants.

It will make a person drunk if he takes a sufficient quant.i.ty of it.

Indeed, it is so like alcohol that it really is a kind of alcohol.