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. Therefore it is that, when there is no
lung, there is also no neck. Of this condition the Fishes are an
example. The other part, or oesophagus, is the channel through which
food is conveyed to the stomach; so that all animals that are
without a neck are also without a distinct oesophagus; Such a part
is in fact not required of necessity for nutritive purposes; for it
has no action whatsoever on the food. Indeed there is nothing to
prevent the stomach from being placed directly after the mouth.
This, however, is quite impossible in the case of the lung. For
there must be some sort of tube common to the two divisions of the
lung, by which--it being bipartite--the breath may be apportioned to
their respective bronchi, and thence pass into the air-pipes; and such
an arrangement will be the best for giving perfection to inspiration
and expiration. The organ then concerned in respiration must of
necessity be of some length; and this, again, necessitates there being
an oesophagus to unite mouth and stomach. This oesophagus is of a
flesh-like character, and yet admits of extension like a sinew. This
latter property is given to it, that it may stretch when food is
introduced; while the flesh-like character is intended to make it soft
and yielding, and to prevent it from being rasped by particles as they
pass downwards, and so suffering damage. On the other hand, the
windpipe and the so-called larynx are constructed out of a
cartilaginous substance
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