. First book in physiology and hygiene . n 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 bones are attachedto the bones by cords called tendons. In the pictureyou can see the tendonsthat fasten one end ofthe muscle to the shoul-der bone, and the tendonthat fastens the other endto the bone of the fore-arm. Each bundle of mus-cle causes only one kindof motion; that is, amotion in one move the par
. First book in physiology and hygiene . n 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 bones are attachedto the bones by cords called tendons. In the pictureyou can see the tendonsthat fasten one end ofthe muscle to the shoul-der bone, and the tendonthat fastens the other endto the bone of the fore-arm. Each bundle of mus-cle causes only one kindof motion; that is, amotion in one move the part of thebody in another direction, another bundle mustshorten up and pull the part with it, while thefirst bundle lensrthens out ao^ain. A muscle cannot be kept shortened any greatlength of time. If you hold your arm bent as longas you possibly can, it feels tired, and finally many of the movements of the body, such aswalkino;, one set of muscles acts while the other setrests, or makes ready to act again. This is the reason. The Mnscles of the Ann contracted tobend it. — 126 — that it is not so tiresome to walk one hour as it is tostand perfectly still for a much shorter time. No part of the body could move without thehelp of muscle. The walls of the stomach are mus-cles, which move and churn the food about. Thewalls of the heart are muscles; their movementpumps the blood through the heart. The esophagusand the intestines are muscles; as one set of musclesafter another contracts, the food is pushed alongthrough the tube. The bony framework, or skel-eton, of the body is covered with muscles that moveit about. The muscles form one-half of the weightof the whole human body, and in it there are morethan five hundred. What we usually call ^ flesh ischiefly muscle and fat. The lean part of beef is theanimals muscle. Clasp your left hand tightly around your rightarm just below the elbow. The muscles that youare pressing control the movements of your you mov
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