A flexible, closed end sheath is first inserted in {HEAD ~ the body} in {TAIL ~ a known way} 
in
A flexible , closed end sheath is first inserted in { HEAD ~ the body } in { TAIL ~ a known way }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL