A complete handbook for the sanitary troops of the U S army and navy . ighteen to the minute. In ordi-nary quiet respirationthe principal muscleconcerned is the diaph-ragm, wliich in its re-laxed state is arched up-ward into the cavity ofthe chest; in its con-traction tlie muscle isflattened out, largely in-creasing the capacity ofthe chest, so that the airrushes in through thelarynx to fill the vacu-um ; inspiration com-pleted, tlie diaphragmrelaxes, the chest wallscollapse, and expirationoccurs. When respira-tion becomes more ac-tive the intercostalmuscles, which raise theribs, come into pla
A complete handbook for the sanitary troops of the U S army and navy . ighteen to the minute. In ordi-nary quiet respirationthe principal muscleconcerned is the diaph-ragm, wliich in its re-laxed state is arched up-ward into the cavity ofthe chest; in its con-traction tlie muscle isflattened out, largely in-creasing the capacity ofthe chest, so that the airrushes in through thelarynx to fill the vacu-um ; inspiration com-pleted, tlie diaphragmrelaxes, the chest wallscollapse, and expirationoccurs. When respira-tion becomes more ac-tive the intercostalmuscles, which raise theribs, come into play,and when still moreeffort is required all themuscles attached to the chest come into action, and even the nostrils are dilated to allow the entrance of-more air. Ordinary outdoor air contains about twenty-one parts of oxygen. seventy-nine parts of nitrogen, and four hundredth parts of carbonic acid, or four parts in ten thotisand. The oxygen is the element of the air which is necessary to sustain life; it serves the same purpose as it does in a fire, maintains the. Fig. 40.— Chest, sliowing Pleura*. 84 ANATOMY AND IllVSJULOGY combustion by which heat and force are produced. If you shut offthe supply of air (oxygen) to a furnace the fire goes out; if you shutoff the supply to the lungs life goes out. The nitrogen has no othervalue than to dilute the oxygen. When air is breathed it loses a portion of its oxygen, is raised intemperature, and has added to it in the lungs carbonic acid, organicmatter, and the vapor of water; the amount of contained carbonicacid is increased a hundred times, to about four per cent. As the air in a confined space is breathed over and over again,headache and drowsiness are experienced, and even death may result. A notable instance of this character occurred in India in the year1756, when one hundred and fifty-six British prisoners were confinedin a dungeon eighteen feet square; the next morning one hundredand twenty-three of them were dead. The cau
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