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