The substantially non dissolvable region remains substantially intact as the dissolving region is progressively dissolved, introducing {HEAD ~ the functional agent} into {TAIL ~ a flowing stream} of water 
into
The substantially non dissolvable region remains substantially intact as the dissolving region is progressively dissolved , introducing { HEAD ~ the functional agent } into { TAIL ~ a flowing stream } of water
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH