This creates {HEAD ~ a pressure difference} between {TAIL ~ the cells} causing the vent follower to move until it arrives at an equilibrium position 
between
This creates { HEAD ~ a pressure difference } between { TAIL ~ the cells } causing the vent follower to move until it arrives at an equilibrium position
OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH