Before revision:  Since the main energetic costs of ventilation are related to the convective transport, we prove that, for all mammals, the localization of the shift from an convective transport into a diffusive transport plays a critical role on keeping that cost low while fulfilling the lung 's function.
After revision:  Since the main energetic costs of ventilation are related to the convective transport, we prove that, for all mammals, the localization of the shift from a convective transport into a diffusive transport plays a critical role on keeping that cost low while fulfilling the lung 's function.