be found to repel one another; but if the north pole of one magnet be brought near the south pole of another magnet they will be found to attract each other. Q. Is the compass used for any other purpose than that of guiding ships? A. Yes; it is used to guide the miner in his subterranean excavations, and the traveller through deserts. Q. Who was the inventor of the mariner's compass? A. It is not known who invented the mariner's compass. THE HUMAN FRAME. Q. What is a skeleton? A. The bones of an animal, separated from the flesh, and preserved in their natural position. Q. What is the skull ? A. The bones which form the exterior of the head, and enclose the brain. The skull consists of the forehead and every part of the head, except the face. Q. What is the spine? A. The spine, or backbone, is a chain of joints made of bone, and extending from the head down to the bottom of the back. Q. How many bones are there in the spine? A. Twenty-four. Q. What are the ribs ? A. The ribs consist of twelve curved bones on each side of the body, which are attached to the spine. Q. What is the chest? A. The chest, or thorax, is formed of the spine on the back part of the body, the ribs on each side, and the sternum. or breast-bone in front. Q. What does the chest, or thorax, contain? A. It contains the heart and lungs. A. The passage for the breath to and from the lungs. Q. What is the gullet? A. The gullet, or esophagus, is the passage by which food and liquid are taken into the stomach. Q. Of what shape is the stomach? A. Its figure has been compared to the figure of the bag or pouch of a bagpipe. Q. Are the passages into the lungs and stomach separate and distinct from each other? A. Yes; they form two distinct passages, the windpipe, or passage into the lungs, being in front of the gullet, or passage into the stomach. Q. Does food and drink, in passing into the stomach, pass over the top of the passage into the lungs ? A. Yes. Q. Since the windpipe is in front of the gullet or œsophagus, how is it that food and drink do not, when we swallow, always pass into the lungs ? A. Because there is a lid over the top of the windpipe, which closes or shuts down when we swallow, to prevent what we eat and drink from passing into the lungs. Q. Does it ever happen that either food or drink passes into the windpipe? A. Yes; and when that is the case, choking arises. The coughing which is produced by choking is an effort of nature to expel or drive out what has passed improperly into the windpipe. Q. What does respiration, or breathing, consist of? A. It consists of inspiration, or drawing in air into the lungs, and expiration, or sending it out of the lungs. During inspiration, the chest expands to receive the air; and during expiration, the chest |