. First book in physiology and hygiene . If you do this, your head hangsforward, your shoulders are round, and your chestis so squeezed in that there is not room enough in itfor all the air you need to breathe. In sleeping, you should not lie with your headraised too high on a thick pillow; for this bendsyour neck and shoulders into an unnatural position. !Mauy boys and girls have misshapen and de-formed bodies because they have not had schoolseats and desks to fit them. If the school seat istoo low or the desk too high, the pupils rightshoulder is raised so much that sitting in this posi-tion
. First book in physiology and hygiene . If you do this, your head hangsforward, your shoulders are round, and your chestis so squeezed in that there is not room enough in itfor all the air you need to breathe. In sleeping, you should not lie with your headraised too high on a thick pillow; for this bendsyour neck and shoulders into an unnatural position. !Mauy boys and girls have misshapen and de-formed bodies because they have not had schoolseats and desks to fit them. If the school seat istoo low or the desk too high, the pupils rightshoulder is raised so much that sitting in this posi-tion will soon deform his spine. If the seat is toohigh or the desk too low, the pupil bends over andbecomes round shouldered. Try to cure yourself of any bad habits of stand-ing or sitting that you may have, such as standingon one foot, walking in a slovenly way, or twistingyourself into awkward positions. We can not ailbe beautiful of face, but most of us can have strong,graceful bodies, if we are careful in using them. XL.—THE MUSCLE:. The ilTiscIes of the Arm. when the ana is extended. ^Vhat do Toii do Tvhen tou ask one of yourschoolmates to •• feel voiir muscle ? You bend your arm at the el-bow and bringyour forearmup as firmly andas far as youcan. And whatis there tofeel? Thereis a bunch un-der the skin at the front of your upper arm; andthe harder the bunch is, the prouder you are of is muscle, and vou are ricrhtlv proud of beincjstrong. How the Muscles Act.—A muscle is made of littletough strings, grouped into a bundle. When youstarted to bend your elbow, each of the tiny threadsof the muscle bundle began to grow shorter andthicker, just as a stretched rubber thread becomesthicker if we let go of one end so that it can goback to its original size. That is, the muscle was 124 — 125 — doing its work by shortening, or contracting. Whena muscle contracts, it pulls on the part of the bodyto which it is attached and makes it move. The muscles that move the bon
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