When the coil is removed from an endoscope, {HEAD ~ the practitioner} or the assistant observes {TAIL ~ the coil} as it is withdrawn and notices the appearance of the stripes as an indication that the distal end of the instrument is not far away 
When the coil is removed from an endoscope , { HEAD ~ the practitioner } or the assistant observes { TAIL ~ the coil } as it is withdrawn and notices the appearance of the stripes as an indication that the distal end of the instrument is not far away
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL 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