nus near F opens into the upper
meatus. The frontal, Z, and maxillary sinuses open into the middle
meatus, and the nasal duct opens into the inferior sinus beneath the
anterior inferior angle of the lower spongy bone, W.

In the living body the very vascular fleshy and glandular Schneiderian
membrane which lines all parts of the nasal fossa almost completely
fills this cavity. When polypi or other growths occupy the nasal fossae,
they must gain room at the expense of neighbouring parts. The nasal duct
may have a bent probe introduced into it by passing the instrument along
the outer side of the floor of the nasal fossa as far back as the
anterior inferior angle of the lower spongy bone, W, at which locality
the duct opens. An instrument of sufficient length, when introduced into
the nostrils in the same direction, will, if passed backwards through
the posterior nares, reach the opening of the Eustachian tube, 8.

While the jaws are closed, the tongue, R, Plate 20, occupies the oral
cavity almost completely. When the jaws are opened they form a cavity
between them equal in capacity to the degree at which they are sundered
from each other. The back of the pharynx can be seen when the jaws are
widely opened if the tongue be depressed, as R, Plate 20. The hard
palate, U, which forms the roof of the mouth, is extended further
backwards by the soft palate, V, which hangs as the loose velum of the
throat between the nasal fossae above and the fauces below. Between the
velum palati, V, and the root of the tongue, we may readily discern,
when the jaws are open, two ridges of arching form, 5, 6, on either side
of the fauces. These prominent arches and their fellows are named the
pillars of the fauces. The anterior pillar, 5, is formed by the
submucous palato-glossus muscle; the posterior pillar, 6, is formed by
the palato-pharyngeus muscle. Between these pillars, 5 and 6, is
situated the tonsil, S, beneath the mucous membrane. When the tonsils of
opposite sides become inflamed and suppurate, an incision may be made
into either gland without much chance of wounding the internal carotid
artery; for, in fact, this vessel lies somewhat removed from it behind.
In Plate 21, that point of the superior constrictor of the pharynx,
marked D, indicates the situation of the tonsil gland; and a
considerable interval will be seen to exist between D and the internal
carotid vessel F.

If the head be thrown backwards the nasal and oral cavitie