and to have been reduced from the flattened span h 2 which preceded the rounding step from this flattened and now also rounded distal end 11 the opposed sidewalls 17 18 are seen in fig4 to spread in progressive definition of the intermediate generally triangular section dimensions which are characterized by the intermediate altitude h 3 and with further progressive section enlargement to a maximum altitude h 4 of generally triangular section magnitude namely at the location of substantial triangular section conformance to the profile fig2 of the glottic opening 14 in close adjacency to the distal end the diverging sidewalls 17 18 are shown with symmetrically opposed ports in the form of longitudinally elongate oval openings 19 20 that are best seen in fig4 and 7 it being noted that in the region between altitudes h 3 and h 4 the symmetrically opposed walls 17 18 will have become components of flat surfaces that are adapted for substantial if not total conformance to contacted divergent inner faces of the vocal cords fig6 and 7 serve to illustrate that for those who prefer the assurance of optical fiber illumination and fiberscope distally directional viewing on the local central axis of the distal end 11 a short central bore 21 in the otherwise closed end 11 will serve to stabilize axially central orientation of optical fiber means 22 inserted via the generally triangular section passage within et tube 10 fig7 further shows inner wall ramp profiling 22 39 convergent to bore 21 whereby to deflect the distal end of the optical fiber means 22 into smooth alignment with and guided entry into the central bore 21 the.