a valve seating portion having a valve opening therein, said {HEAD ~ valve opening} permitting {TAIL ~ serum} or plasma to flow into said tubular member when the separator tube is plunged into the collection tube, 
permitting
a valve seating portion having a valve opening therein , said { HEAD ~ valve opening } permitting { TAIL ~ serum } or plasma to flow into said tubular member when the separator tube is plunged into the collection tube ,
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD 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