against time in the experiment the volume data was computed integrated from the airflow measurement the two panels are two ways of looking at the same data collected at the same time in each panel the dotted tracing 500 in 5 b and 502 in panel 5 a represent the normal or natural or not stimulated and therefore underlying breathing pattern of the animal in panel 5 a the inspiration phase of tracing 502 is seen as segment 514 after tracing 502 peaks the expiration phase begins as indicated by segment 516 the figure shows that along trace 502 the air that is inhaled is exhaled before 2 seconds has elapsed as indicated by the dotted trace 502 returning to the zero volume level trace 504 is associated with the unilateral delivery of stimulation 508 to a phrenic nerve in the tracing the start of stimulation at time 518 is well after the start of inspiration and corresponds approximately to the reversal of airflow from inspiration to expiration as seen at time 518 very shortly after the stimulation begins the animal inhales more air seen by the u201c bump u201d 520 in the tracing 504 in panel 5 b a small increment in the total volume corresponding.