The body cavity of chicken under anesthesia was opened, and then the state of breathing and activities of air sac wal were observed. The results showed that, although the body cavity was opened, the chicken could stil breathe. When the chicken breathed in, the chest sidewal , thoracico-abdominal diaphragm and lung diaphragm al initiatively became larger, inflating the prethoracic and metathoracic air sacs; the cervical, clavicular and abdominal air sac wal s al contracted, shrinking the air sacs. When the chicken breathed out, the chest sidewal , thoracico-ab-dominal diaphragm and lung diaphragm initiatively contracted, shrinking the pretho-racic and metathoracic air sacs; the cervical, clavicular and abdominal air sac wal s al expanded, expanding the air sacs. Therefore, the chicken could stil breathe after the body cavity was opened. When the chicken breathed in, the prethoracic and metathoracic air sacs were al expanded, and the air flowed from the cervical, clav-icular and abdominal air sacs and respiratory tract to the prethoracic and metatho-racic air sacs through the lung, shrinking the cervical, clavicular and abdominal air sacs; when the chicken breathed out, the prethoracic and metathoracic air sacs wal s al contracted, and the air was extruded from the prethoracic and metathoracic air sacs into the cervical, clavicular and abdominal air sacs and respiratory tract trough the lung, expanding the cervical, clavicular and abdominal air sacs. During the entire breathing process, the prethoracic and metathoracic air sacs al can ex-pand and shrink initiatively, making the air flow though the lung.
