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