sists in a particular mode of nerve termination.

The tongue is a muscular organ covered with mucous membrane, and is
richly supplied with blood-vessels and nerves. By its complicated
movements it is an important factor in chewing, in swallowing, and in
articulate speech. The surface of the tongue is covered with irregular
projections, called papillae,--fine hair-like processes, about 1/12 of
an inch high. Interspersed with these are the fungiform papillae.
These are shaped something like a mushroom, and may often be detected by
their bright red points when the rest of the tongue is coated.

Towards the root of the tongue is another kind of papillae, the
circumvallate, eight to fifteen in number, arranged in the form of
the letter V, with the apex directed backwards. These are so called
because they consist of a fungiform papilla surrounded by a fold of mucous
membrane, presenting the appearance of being walled around.

In many of the fungiform and most of the circumvallate papillae are
peculiar structures called taste buds or taste goblets. These
exist in great numbers, and are believed to be connected with nerve
fibers. These taste buds are readily excited by savory substances, and
transmit the impression along the connected nerve.

The tongue is supplied with sensory fibers by branches from the fifth and
eighth pairs of cranial nerves. The former confers taste on the front part
of the tongue, and the latter on the back part. Branches of the latter
also pass to the soft palate and neighboring parts and confer taste on
them. The motor nerve of the tongue is the ninth pair, the hypoglossal.

[Illustration: Fig. 125.--The Tongue.

A, epiglottis;
B, glands at the base of tongue;
C, tonsil;
D, median circumvallate papilla,
E, circumvallate papillae;
F, filiform papillae;
H, furrows on border of the tongue;
K, fungiform papillae.
]

318. The Sense of Taste. The sense of taste is excited by stimulation
of the mucous membrane of the tongue and of the palate, affecting the ends
of the nerve fibers. Taste is most acute in or near the circumvallate
papillae. The middle of the tongue is scarcely sensitive to taste, while
the edges and the tip are, as a rule, highly sensitive.

Certain conditions are necessary that the sense of taste may be
exercised. First, the substance to be tasted must be in _solution_, or be
soluble in the fluids of the mouth. Insoluble substances are tasteless. If
we touch our to