Identifier: physiologyhygien00heiz (find matches)
Title: Physiology, hygiene and sanitation, an elementary textbook of physiology, with special attention given to hygiene and sanitation
Year: 1919 (1910s)
Authors: Heizer, W. L. (W. Lucien), b. 1880
Subjects: Physiology Hygiene Sanitation
Publisher: Louisville, Ky., C.T. Dearing Printing Co., Incorporated
Contributing Library: The Library of Congress
Digitizing Sponsor: The Library of Congress

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e are covered with a synovialmembrane. To prevent friction and insure a smooth, noiseless work-ing of the bones the synovial membrane and the tendonsworking over the joints are kept lubricated, oiled, bysynovial fluid. Structure of Bones. In early childhood the bones aremuch more soft and spongy than in later years. This isa wise provision of nature to protect the child, for the bones being spongywill not break aseasily as if they werehard and brittle likea piece of chalk. Inold age a slight fallwill often cause aserious break in abone because theanimal matter whichgives to the bone itselasticity in youthhas largely disappeared and it is composed mostly ofmineral matter which is hard and brittle. If a fresh boneis put into a grate of live coals for an hour, the animalmatter will be consumed and the bone will consist of min-eral matter when it may be easily crushed like chalk. If a bone be soaked for several days in strong vinegaror diluted muriatic acid, the mineral matter will be re-
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Fig-. 18.—A thin slice of bone greatlymagnified showing the canals andpassages for the nerves and bloodvessels. A. Haversian canal. THE OSSEOUS SYSTEM—THE SKELETON 49 moved and the bone may be bent or eVen tied in a knotbecause it contains mostly the animal matter. A bone when sawed across is seen to be hollow and tocontain fat which is called marrow. Blood vessels andnerves are also found in bone marrow. It is found to bespongy and filled with tiny holes. These are the mouthsof the Haversian Canals which in health allow blood ves-sels and nerves to reach every part of a bone. If a thin piece of bone not larger than the head of apin be put under the microscope, these tiny canals maybe seen and even smaller ones branching out to feed thebone cells of which every bone is composed. Summary Giving to the body its shape and support, protectingdelicate organs, and serving as levers for the action ofmuscles, comprise the three most important uses of theskeleton. Bones are short, long, fl

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