An elementary physiology and hygiene for use in upper grammar grades . ze and of them are fastened to at least two bones, so FRAMEWORK AND MOTION OF THE BODY 147 that as the muscles are contracted the bones are 56 and 59 show how the muscles are arrangedin the body, though compara-tively few are representedhere. The various musclesare so attached to the bonesthat they can be moved inall the directions that thejoints permit. We can bendthe arm or straighten it; wecan move it to either side orturn it around, each motionbeing produced by a differentset of muscles. Muscle
An elementary physiology and hygiene for use in upper grammar grades . ze and of them are fastened to at least two bones, so FRAMEWORK AND MOTION OF THE BODY 147 that as the muscles are contracted the bones are 56 and 59 show how the muscles are arrangedin the body, though compara-tively few are representedhere. The various musclesare so attached to the bonesthat they can be moved inall the directions that thejoints permit. We can bendthe arm or straighten it; wecan move it to either side orturn it around, each motionbeing produced by a differentset of muscles. Muscle Growth. — It is apeculiarity of muscles thatthe more they are used, thestronger they grow. Theblacksmith, because he con-stantly swings his heavyhammer, develops very strongmuscles in his arms. Whena person learns to ride abicycle, he finds that certainmuscles of his legs are weak,but, as he continues the exer-cise, the muscles becomestronger, until he can climbeven high hills without any great strain. One set ofmuscles, however, should not be developed and others. Fig. 59. —The Surface Mus-cles of the Body. 148 PHYSIOLOGY AND HYGIENE neglected. The man who has all his muscles moderatelywell developed is stronger and more healthy than theone who has highly developed his arm muscles with-out exercising equally the other muscles of the body. If muscles are not used, they become small andweak. If a muscle were left idle for a few months, itwould lose much of its power, so that we could not useit at all. Children in their active play ordinarily useall their muscles, so that they develop evenly. Butas people grow older, certain muscles are used less andless. We take the trolley-car and the elevator to savethe trouble of walking: as a result, we find that wecannot walk so far as we could a few years ago. We usethe right hand in our work rather than the left, andthe left hand is weaker and less skillful. We sit in acomfortable easy-chair until the muscles of the back areweakened,
Size: 936px × 2670px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, booksubjectphysiology, bookyear1
