7.  The Clothing.—­The skin should be protected by proper clothing, but it is not well to wear more than is necessary, as it makes the skin so sensitive that one is liable to take cold.

8.  The Proper Temperature of Rooms.—­It is also very unwise for a person to keep the rooms in which he lives too warm, and to stay too much in-doors, as it makes him very liable to take cold when he goes out-of-doors.  One who is out of doors in all kinds of weather seldom takes cold.

9.  Care of the Hair and the Nails.—­The scalp should be kept clean by thorough and frequent washing and daily brushing.  Hair oils are seldom needed.  If the skin of the head is kept in a healthy condition, the hair requires no oil.

10. The habit of biting and picking the fingernails is a very unpleasant one, and keeps the nails in a broken and unhealthy condition.  The nails should be carefully trimmed with a sharp knife or a pair of scissors.

11.  Effects of Narcotics and Stimulants upon the Skin.—­Alcohol, tobacco, opium, and all other narcotics and stimulants have a bad effect upon the skin.  Alcohol often causes the skin to become red and blotched, and tobacco gives it a dingy and unhealthy appearance.

SUMMARY.

1.  If the pores of the skin are closed, a person will die.

2.  We should bathe often enough to keep the skin clean.

3.  We should not keep our rooms too warm, and should avoid wearing too much clothing.

4.  Alcohol, tobacco, and other stimulants and narcotics injure the skin.

CHAPTER XVII.

THE KIDNEYS AND THEIR WORK.

1.  The Kidneys.—­The kidneys are among the most important organs of the body.  They are in the cavity of the abdomen, near the back-bone, up under the lower border of the ribs.  Perhaps you have seen the kidneys of a sheep or a hog.  If you have, you know very nearly how the kidneys of our own bodies appear.

[Illustration:  KIDNEY.]

2.  The Work of the Kidneys.—­The work of the kidneys is to separate from the blood certain very poisonous substances, which would soon cause our death if they were not removed.  It is very important to keep these useful organs in good health, because a person is certain to die very soon when the kidneys are in any way seriously injured.

3.  How to Keep the Kidneys Healthy.—­One way of keeping the kidneys in good health is to drink plenty of pure water, and to avoid eating too much meat and rich food.  Pepper, mustard, and other hot sauces are very harmful to the kidneys.

4.  Importance of Keeping the Skin Clean.—­The work of the kidneys is very similar to that of the skin; and when the skin does not do its full duty, the kidneys have to do more than they should, and hence are likely to become diseased.  For this reason, persons who allow their skins to become inactive by neglecting to bathe frequently are apt to have disease of the kidneys.