. First book in physiology and hygiene . h the wall of a bloodvessel and busy themselves in the flesh near by, eat-ing up waste bits or disease germs there. If you scratch or cut your finger, and a littledirt gets into the cut, a great number of whiteblood corpuscles ^rush to the scene of the acci-dent, as it were. They try to devour any germsthat have come in with the dirt, and they try topush out of the sore any matter that they cannotabsorb. If the finger is inflamed, or white [festered) — 85 — around the edges of the cut, you may know thatthere is a hard fight going on between the poisonge
. First book in physiology and hygiene . h the wall of a bloodvessel and busy themselves in the flesh near by, eat-ing up waste bits or disease germs there. If you scratch or cut your finger, and a littledirt gets into the cut, a great number of whiteblood corpuscles ^rush to the scene of the acci-dent, as it were. They try to devour any germsthat have come in with the dirt, and they try topush out of the sore any matter that they cannotabsorb. If the finger is inflamed, or white [festered) — 85 — around the edges of the cut, you may know thatthere is a hard fight going on between the poisongerms and the white cells of the blood. It is bestto save this trouble by washing a cut or wound ofany kind in clean water as soon as possible, andbefore it is bound up. XXIX.—HOW THE BLOOD CIRCULATES. How the Blood Travels.—As the blood must flowup to your head as well as down to your feet, it hasto be pumped to keep it moving. The pump is theheart. The blood passes through the body in tubes or blood vessels of difierent WINDPIPE. sizes. The tubes throughwhich the blood is car-ried out from the heartto the various parts ofthe body are called arter-ies. The tubes throughwhich the blood flowsback to the heart arecalled veins. The arteries are quite large near the heart, butthey soon divide into branches. These branchesdivide again and again, until they are very smalland thread-like. These finest branches are calledcapillaries. They are everywhere in the body,around the bones and nerves and muscles. Thewalls of the capillaries are very thin. Some of the 86 — 87 — blood soaks through the sides of the tubes and sup-pUes the near-by parts of the body with food, whichthey are always ready to take in and use. At the same time that the blood in the capil-laries is unloading food, it is loading up with wastematter. The capillaries join again to form largertubes, the veins. As the veins get nearer to theheart, the smaller veins come together to makelarger veins. These in turn i
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