These valves are closed when the separator tube 16 is inserted into the collection tube 10 as shown in FIG 7, but opened as the separator tube 18 is removed from the collection tube 10 as shown in FIG 7a so as to allow {HEAD ~ air} to enter {TAIL ~ the collection tube} 
to enter
These valves are closed when the separator tube 16 is inserted into the collection tube 10 as shown in FIG 7 , but opened as the separator tube 18 is removed from the collection tube 10 as shown in FIG 7a so as to allow { HEAD ~ air } to enter { TAIL ~ the collection tube }
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 OTH OTH HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL