The counter force of the vacuum resists {HEAD ~ tissue movement} in the direction of {TAIL ~ electrode penetration} 
The counter force of the vacuum resists { HEAD ~ tissue movement } in the direction of { TAIL ~ electrode penetration }
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL