{HEAD ~ A ring} applied to the surface of the tissue stabilizes the tissue to the optics and localizes {TAIL ~ a portion} of the tissue surface through an aperture in the ring 
localizes
{ HEAD ~ A ring } applied to the surface of the tissue stabilizes the tissue to the optics and localizes { TAIL ~ a portion } of the tissue surface through an aperture in the ring
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH