. Kirkes' handbook of physiology . n that ofexpiration, and there is commonly a very slight pause between the end ofexpiration and the beginning of the next inspiration, see figure 232. Theratio of the respiratory rhythm may be thus expressed: Inspiration 6 Expiration 7 to 8 Pause Very slight QUANTITY OF AIR BREATHED 259 If the ear be placed in contact with the wall of the chest, or be separatedfrom it only by a good conductor of sound or a stethoscope, a faint respiratorymurmur is heard during inspiration. This sound varies somewhat in differentparts, being loudest or coarsest in the neighbor
. Kirkes' handbook of physiology . n that ofexpiration, and there is commonly a very slight pause between the end ofexpiration and the beginning of the next inspiration, see figure 232. Theratio of the respiratory rhythm may be thus expressed: Inspiration 6 Expiration 7 to 8 Pause Very slight QUANTITY OF AIR BREATHED 259 If the ear be placed in contact with the wall of the chest, or be separatedfrom it only by a good conductor of sound or a stethoscope, a faint respiratorymurmur is heard during inspiration. This sound varies somewhat in differentparts, being loudest or coarsest in the neighborhood of the trachea and largebronchi (tracheal and bronchial breathing), and fading off into a faint sighingas the ear is placed at a distance from these (vesicular breathing). It isheard best in children. In them a faint murmur is heard in expiration cause of the vesicular murmur has received various explanations. Most button. Tube to commu-nicate with re-cording tam-bour, Ball to fill appa- _ratua with air. Fig. 233.—Stethometer. (Burdon-Sanderson.) observers hold that the sound is produced in the glottis and larger bronchialtubes, but that it is modified in its passage to the pulmonary alveoli. Indisease of the lungs the vesicular murmur undergoes various modifica-tions, for a description of which one must consult text-books on physicaldiagnosis. The Quantity of Air Breathed. Tidal air is the quantity of airwhich is habitually and almost uniformly changed in each act of a healthy adult man it is about 30 cubic inches, or about 500 or halfa liter. In college students the tidal air is somewhat less, varying from 300to 400 The Complemental Air is the quantity of air which can be drawn into thelungs by the deepest inspiration over and above that which is in the lungs 260 RESPIRATION at the end of an ordinary inspiration. Its amount varies, but may be reck-oned as ioo cubic inches, or about 1,600 The Reserve Air is that which m
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