Studies on the role of air-sacs in respiration and on the paths of air-flow between lungs and air-sacs in some birds

Abstract

This investigation was carried out to clarify the role of air-sacs in respiration and the paths of air-flow between lungs and air-sacs in some birds.Birds used for the present investigation were domestic fowl (Gallus domesticus), guinea fowl (Numida meleagris), domestic duck (Anas platyrhyncha), turkey (Meleagris gallopavo), black-eared kite (Milvus migrans), white king dove (Columba livia var. domesticus) and pigeon (Columba livia).The results obtained are summarized as follows.I. From the observation of the longevity of white-king dove and domestic fowl under the condition of the artificially destroyed lungs or air-sacs, the following results are obtained. i) When all the air-sacs were destroyed and both the lungs were removed from the ribs, the birds died suddenly. ii) When all the air-sacs were destroyed and the lungs were remained in normal condition, the birds died after a while. iii) The birds with the lungs and some undamaged air-sacs survived always longer than any of the above mentioned cases. iv) The air-flow in bronchi which connect directly to air-sacs changed the direction after the destruction of the air-sacs. These results seem to suggest the following facts. Although lungs can actively ventilate independently of air-sacs, it is impossible to maintain the life of birds for a long time owing to a small quantity of air in the lungs. The ventilation of lungs is promoted by air-sacs. Finally, the direction of the air-flow between lungs and air-sacs is mainly controlled by the air sacs.II. The following became clear after the measurement of the air-pressure in the air-sacs and bronchi of domestic duck, black eared kite and white-king dove. The change of the air-pressure in those organs is always synchronized with the respiratory movement of the birds. The maximum negative pressure at the most expanded thorax is usually not equal in absolute value to the maximum positive pressure at the contrary position of the thorax.III. In domestic fowl, domestic duck, turkey, guinea fowl, white king dove and pigeon, the air included in the air-sacs was peculiar to the kind of the air-sacs in the composition such as the rate of O2 and CO2. Difference between the expired air and the inspired one in an air-sac, however, was not conspicuously recognized in the composition.IV. The domestic fowl, domestic duck, turkey, guinea fowl and pigeon were ligated the trachea and opened the interclavicular air sac. The birds under the such condition lived for a long time. The respiratory rate, howewer, increased, and then the air in the air-sacs changed in the composition.V. In domestic duck and black-eared kite observations through the injection of alminium powder into the air-sacs and the measurment of the air-pressure in the bronchi and air-sacs were ascertained that the direction of the air-flow between the lung and air-sacs was reversed with each phase.