{TAIL ~ A fresh supply} of solution to the face of {HEAD ~ the membrane} is provided by a stirrer 
{ TAIL ~ A fresh supply } of solution to the face of { HEAD ~ the membrane } is provided by a stirrer
TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH