{HEAD ~ One end} of the tube 44 is in {TAIL ~ communication} with a central portion of the tube 45, and the other end of the tube 44 is formed with a gas supply hole 41 
is in
{ HEAD ~ One end } of the tube 44 is in { TAIL ~ communication } with a central portion of the tube 45 , and the other end of the tube 44 is formed with a gas supply hole 41
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH REL REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH