Physiology and biochemistry in modern medicine . r of adrum. The spirometers are connected so that the air current may be directed in thethree following ways: (1) through Cocks 1 and 2 outside; (2) directly through bothcocks into the large spirometer for the purpose of collecting a series of expirations;and (3) through Cock 1 directly into the small spirometer for catching a single expira-tion. In all experiments the first tilling of the spirometer is rejected, so that the deadspace of the spirometers is filled with air of approximately the same composition as inthe succeeding expirations. The
Physiology and biochemistry in modern medicine . r of adrum. The spirometers are connected so that the air current may be directed in thethree following ways: (1) through Cocks 1 and 2 outside; (2) directly through bothcocks into the large spirometer for the purpose of collecting a series of expirations;and (3) through Cock 1 directly into the small spirometer for catching a single expira-tion. In all experiments the first tilling of the spirometer is rejected, so that the deadspace of the spirometers is filled with air of approximately the same composition as inthe succeeding expirations. The time is marked in seconds by a time dock. The respira-tory movements are recorded by a pneumograph. (Fig. 128.) The subject is brought into respiratory equilibrium by having him breathe throughthe valves for a period of time before the observation. The respiratory movementsduring this time are recorded while the cocks are in Position 1. When the observationis started, the cocks are turned into Position 2 during the time an inspiration is being. Fig. 128.—Arrangement of meters and connections of Pearces method for measurement of C02 of alveolar air in normal subjects. made, so that the expirations which follow may be collected in the large about ten respirations (a counted number) have been collected, the cocks areturned to Position 3 during an inspiration, and a single deep expiration is collectedin the small spirometer. In order that the time of this may be the same as the normalexpiration, it is necessary to quicken it. This is more or less a chance procedure, butwith a little training, the operator can close the stopcock with sufficient accuracy tointerrupt the deep expiration at the end of the normal expiratory time. Shouldthere be any gross variation from the normal expiratory time, the sample must be col-lected again. Not infrequently the inspiration immediately preceding the expirationinto the small spirometer is varied involuntarily by the subject on
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