In betwixt the two openings

comes the so-called epiglottis, an organ capable of being drawn over
and covering the orifice of the windpipe communicating with the mouth;
the end of the tongue is attached to the epiglottis. In the other
direction the windpipe extends to the interval between the lungs,
and hereupon bifurcates into each of the two divisions of the lung;
for the lung in all animals possessed of the organ has a tendency to
be double. In viviparous animals, however, the duplication is not so
plainly discernible as in other species, and the duplication is
least discernible in man. And in man the organ is not split into
many parts, as is the case with some vivipara, neither is it smooth,
but its surface is uneven.