a movable valve member adapted to seat on said seating portion on one side of said opening so as to close {TAIL ~ said valve opening} in the presence of {HEAD ~ serum} or plasma in said tubular member, 
a movable valve member adapted to seat on said seating portion on one side of said opening so as to close { TAIL ~ said valve opening } in the presence of { HEAD ~ serum } or plasma in said tubular member ,
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH