Video 2

Movie S2. In vivo visualization of synthetic smoke showing tidal flow. Endoscopic video (left circle) of synthetic smoke moving in the caudal chamber of a green iguana at the plane illustrated in Fig. 2 D and E. During exhalation particles of smoke move at slow speed craniad (toward the upper left-hand corner of the field of view). During inhalation a high-velocity stream of smoke emanates rapidly caudad (toward the lower right hand field of view). Airflow at the nares was measured with a pneumotachograph (right panel). Expiration is negative.