{TAIL ~ The applied field} comprises a first, external magnetic gradient which moves magnetically responsive particles to {HEAD ~ a region} of a collection vessel 
{ TAIL ~ The applied field } comprises a first , external magnetic gradient which moves magnetically responsive particles to { HEAD ~ a region } of a collection vessel
TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH