Fig. 2. Ensemble averages of electromyographic (EMG) activity of nine trunk muscles from a single dog standing and panting, revealing a ventilatory function for all muscles except the longissimus dorsi and deep pectoralis. Only the external intercostal and parasternal internal intercostal have an inspiratory function. Muscles that were active were not all active at the same time. Ventilatory airflow traces are shown below for reference. Exp., expiration; Insp., inspiration. All traces are on the same time scale. See text for discussion.