The plug comprises a valve seating portion having {HEAD ~ a valve opening} therein and 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 {TAIL ~ the collection tube} 
The plug comprises a valve seating portion having { HEAD ~ a valve opening } therein and 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 { TAIL ~ the collection tube }
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD 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 OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL