The plug comprises {HEAD ~ a valve seating portion} having a valve opening therein and {TAIL ~ a valve head} adapted to seat on the seating portion and bias means extending between the seating portion and the valve head to bias the head to the seated position on the seating portion when the separator tube is stationary within the collection tube 
The plug comprises { HEAD ~ a valve seating portion } having a valve opening therein and { TAIL ~ a valve head } adapted to seat on the seating portion and bias means extending between the seating portion and the valve head to bias the head to the seated position on the seating portion when the separator tube is stationary within the collection tube
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL OTH OTH OTH OTH OTH TAIL TAIL 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 OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH