Man was given a neck for the sake of the lungs
That a neck was given mankind for the sake of the lungs is best proven
by the fact that it is always missing when there are no lungs. For example,
this is the reason fish (which also have no lungs) have no neck. Those animals
to which Nature gave lungs are also endowed with a neck.
For it was necessary that the
[trachea] (shown in fig. 1, ch. 38;
vessels running through the neck and lungs are seen in the figure at the end of
Bk. 3 and the one attached to the end of Bk. 4), through which we bring air
into the lungs when we inhale and blow it out again when we exhale, run from
the mouth to the lungs, and for this reason that a space intervene between
mouth and lungs, since it was fitting that man be endowed with adequate
(which is the material of the voice).
For the voice is impossible without benefit of the rough artery. Therefore we
do not wonder that no animal without a neck emits a voice.