The Movement of Gas in the Respiratory System of the Duck

Abstract

1. A single inhalation of marker gas (argon) was administered to unanaesthetized ducks. Pargon was continuously monitored in the interclavicular, cranial thoracic, caudal thoracic and abdominal air sacs with a mass spectrometer during the marked inspiration and subsequent respiratory cycles. 2. The sequence of arrival times of the inspired marker at the various sampling sites was determined; ventilation rates of the different air sacs were compared by examining the rate of decrease of Par during washout of each sac. 3. The experimental results agree with previously proposed patterns of air flow in the duck respiratory system. 4. It is proposed that the movement of gas in the respiratory system of birds is a two-cycle event. During the inspiratory phase of the first cycle, inhaled air is drawn into the posterior air sacs; during the expiratory phase of the first cycle, this air (having mixed with the residual air in the posterior air sacs) is pumped into the secondary and tertiary bronchi of the lung; during the inspiratory phase of the second cycle this air in the lung passage-ways is drawn into the anterior air sacs; and finally, during the expiratory phase of the second cycle, this air is exhaled from the anterior air sacs and the respiratory system.