5.  Effects of Alcohol and Tobacco upon the Kidneys.—­A piece of beef placed in alcohol soon becomes dry and hard, and shrivels up as though it had been burned.  The effect upon the kidneys of drinking strong liquor is almost the same.  Beer and hard cider also do the kidneys harm, sometimes producing incurable disease of these important organs.

SUMMARY.

1.  The kidneys somewhat resemble the skin in their structure and in their work.

2.  The kidneys remove from the blood some poisonous substances.

3.  To keep the kidneys healthy we should drink plenty of water, avoid irritating foods and drinks, and keep the skin in health by proper bathing.

4.  The drinking of strong liquors often causes incurable disease of the kidneys.

CHAPTER XVIII.

OUR BONES AND THEIR USES.

1.  The Bones.—­In an earlier chapter we learned something about the bones.  This we must try to recall.  You will remember that we called the bones the framework of the body, just as the timbers which are first put up in building a house are called its frame.

2.  The Skeleton.—­All the bones together make up the skeleton. (See page 95.) There are about two hundred bones in all.  They are of many different shapes.  They vary in size from the little bones of the ear, which are the smallest, to the upper bone of the leg, which is the largest in the body.

3. The skeleton is divided into four parts:  the skull, the trunk, the arms, and the legs.  We must learn something more about the bones of each part.

4.  The Skull.—­The skull is somewhat like a shell.  It is made of a number of bones joined together in such a way as to leave a hollow place inside to hold the brain.  The front part of the skull forms the framework of the face and the jaws.  In each ear there are three curious little bones, which aid us in hearing.

5.  The Trunk.—­The bones of the trunk are, the ribs, the breast-bone, the pelvis, and the back-bone.  The bones of the trunk form a framework to support and protect the various organs within its cavities.

6.  The Ribs.—­There are twelve ribs on each side.  The ribs join the back-bone at the back.  They are connected by cartilage to the breast-bone in front.  They look somewhat like the hoops of a barrel.  With the breast-bone and the back-bone they form a bony cage to contain and protect the heart and the lungs.

7.  The Pelvis.—­The pelvis is at the lower part of the trunk.  It is formed by three bones, closely joined together.  The large bones at either side are called the hip-bones.  Each hip-bone contains a deep round cavity in which the upper end of the thigh-bone rests.

8.  The Back-bone.—­The back-bone, or spinal column, is made up of twenty-four small bones, joined together in such a way that the whole can be bent in various directions.  The skull rests upon the upper end of the spinal column.  The lower end of the back-bone forms a part of the pelvis.