Movie 3.

Lung ventilation with a blood pressure cuff applied to the 296 vascular region in boa03. A blood pressure cuff is applied around the vascular portion 297 of the lung and ribs in the anterior region (teal) do not rotate (upper graph). Ribs in the 298 posterior saccular region (gold) rotate substantially (middle graph). Airflow is recorded 299 with pneumotachography (bottom graph) and airflow into the saccular region is visible as 300 the ribs expand. In contrast to the dark radio dense body of the snake, air is visible as 301 white on the x-ray images. Note that there are no rib motions occurring between the two 302 sets of ribs, indicating discrete relocation of lung ventilation from the vascular region to 303 the saccular region.