Occasionally, {HEAD ~ control} of {TAIL ~ the treating solution flow} in addition to that provided by the brush members is necessary 
of
Occasionally , { HEAD ~ control } of { TAIL ~ the treating solution flow } in addition to that provided by the brush members is necessary
OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH