File:Keeping physically fit; common-sense exercises for the whole family (1916) (14594986749).jpg

Identifier: keepingphysicall00crom (find matches)
Title: Keeping physically fit; common-sense exercises for the whole family
Year: 1916 (1910s)
Authors: Cromie, William J. (William James), 1877-
Subjects: Physical education and training
Publisher: New York, The Macmillan company
Contributing Library: The Library of Congress
Digitizing Sponsor: The Library of Congress

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s one of the great-est factors in keeping fit physically. The Breathing Organs In order that the act of breathing may bebetter understood, I shall give a short reviewof the physiology of the chest and lungs. Thelungs, or organs of respiration, with the heartbetween them, are situated in the thorax orchest and are separated from the stomach andintestines and other organs of the abdomen bythe broad umbrella-shaped bridge, or muscleextending across the body, called the diaphragm.When one is about to inhale air, the muscularfibers in this membrane contract in such a man-ner as to bring the diaphragm more nearly to alevel or plane than it was before, enlarging thecavity of the chest and thus causing a negativepressure, often spoken of as a ^vacuum/ Theair rushes through the mouth and nostrils,^ tra-chea or windpipe, and bronchial tubes, to equal-ize the pressure in the lungs with that outside.This is called in-breathing, or inspiration. Out-breathing, or the act of expiration, is caused by
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94 Keeping Physically Fit the diaphragms being pushed upward againstthe lungs by the contraction of the musclesof the abdomen; the walls of the chest con-tract, the ribs being pulled downward by themuscles. The size of the chest is greatly diminished bythese movements, and the air is pressed out ofthe lungs through the air-tubes, bronchi, larjoix,and nostrils. For the function of breathing,one possesses a bellows-like arrangement whichalternately contracts and expands under thecontrol of the nervous system, bearing a closeanalogy in its mode of action to the apparatusemployed in the circulation of the blood. Eachconsists essentially of a kind of pump whichpropels one fluid, and the other air, through aseries of ramified tubes, the difference beingthat in the lungs the inflow and outflow pipesare the same. Although one can breathe through either themouth or the nostrils, the latter are the naturalair-passages, inasmuch as they are always open.The larynx or opening into the windpipe is

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