File:Physiology, hygiene and sanitation, an elementary textbook of physiology, with special attention given to hygiene and sanitation (1919) (14785023923).jpg

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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Text Appearing Before Image:
ight lung. B.Left lung. C. The pericardium containingthe heart. 170 PHYSIOLOGY, HYGIENE AND SANITATION stances, is filled with air and is so light that it floats in water. The lungs are penetrated in every direction by the bron-chial tubes, which branch from each bronchus, like the branches of a tree.These tubes finally become so small that their branches may be likened to the twigs of a tree that send forth stems; and finally they end in the air sacs of the lungs. These air sacs are sosmall thatabout fivemill ion ofthem wouldbe found in apair of lungs,and if theirwalls couldbe spread outon a flat sur-face andplaced to-gether as in acrazy quiltor bed cover,their surfacewould be as large as a rug four feet wide and five feet long, or twenty square feet. It is in the air sacs that the exchange of oxygen and carbon dioxide is made. The lungs are covered with a smooth, velvety lining or cover called the pleura. The pleura also winds around and covers the inside surface of the chest walls.
Text Appearing After Image:
Fig\ 73.—Showing- the Trachea, A. Rig-ht bron-chus, B. Left bronchus, C. and bronchialtubes as they subdivide from each bronchus.Note the rings of cartillagre (gristle) in the larg--est tubes. THE LUNGS 171 The space formed by the ribs and breast bone (thesternum) in front, and the upper part of the backbone(spinal column) behind, is called the thoracic cavityand a cage or frame forming its walls is called the thorax. The thoracic cavity is mostly occupied by the lungs andthe heart. The outer walls of the lungs lie in close contact withthe inner walls of the thoracic cavity. The layers ofpleura are, therefore, in contact and as the walls move toand fro, in breathing, the layers of pleura rub over oneanother. Nature pro-vides a fluid to pre-vent friction and ir-ritation of the pleura. If an infection ofthe pleura occur,such an inflamma-tion resulting is call-ed pleurisy, and isexceedingly painful,because, with eachrespiration, the sen-sitive nerves are rubbed together. How We Breathe

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