SENSE OF TASTE.
865. The chief organ of TASTE is the upper surface of the tongue;
though the lips, the palate, the internal surface of the cheeks, and
the upper part of the oesophagus, participate in this function.
ANATOMY OF THE ORGANS OF TASTE.
866. The tongue is a double organ, composed chiefly of muscular
fibres, which run in almost every direction. The two sides are so
perfectly distinct, that sometimes, in paralysis, one side is
affected, while the function of the other remains perfect. It
possesses great versatility of motion, and can be moulded into a great
variety of shapes. In articulation, mastication, and deglutition, the
tongue is an auxiliary to other organs.
867. This organ is abundantly supplied with blood-vessels, having a
large artery sent to each side of it. It is also very largely
furnished with nerves; it receives nervous filaments from the fifth,
ninth, and twelfth pairs of nerves. The branch of the fifth, called
the gustatory, is the nerve of taste and sensibility;[21] the
twelfth, called the hypo-glossal, of voluntary motion. By means of the
ninth, called the glosso-pharyngeal the tongue is brought into
association with the fauces, oesophagus, and larynx. It is of obvious
importance that these parts should act in concert; and this is
effected by the distribution of this nerve.
[21] Some physiologists impute the sense of taste to the ninth pair of
nerves; others, to the twelfth pair; while others, again,
contend that taste is the result of a concurrent action of the
fifth, ninth, and twelfth pairs of nerves.
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865. What is the chief organ of taste? What other parts participate in
the function? 866-870. _Give the anatomy of the organs of taste._ 866.
Give the structure of the tongue. 867. Is this organ abundantly
supplied with blood? From what source does the tongue derive its
nerves?
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[Illustration: Fig. 134. A view of one side of the neck, showing the
nerves of the tongue. 1, A fragment of the temporal bone. 2, 3, 4, 6, 7,
8, 9, 10, 11, 12, Muscles of the tongue, fauces, and neck. 5, The tongue.
13, The common carotid artery. 14, The jugular vein. 15, The external
carotid. 16, The internal carotid. 17, The gustatory branch of the fifth
pair of nerves. 20, The glosso-pharyngeal nerve. 21, The hypo-glossal, or
the muscular nerve of the tongue. 24, The pneumogastric nerve. 25, The
facial nerve.]
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868. What is the appearance of the surface of the tongue? Explain fig.
134.
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868. The surface of the tongue is thickly studded with fine papillae,
or _vil'li_, which give the organ a velvety appearance. These papillae
are of three varieties. The first is situated near the base of the
tongue. They belong to the class of mucous follicles. They are larger
than the others, and are called _len-tic'u-lar_, from being shaped
like a lens. These, together with the tonsils, (sometimes called the
almonds of the ears,) secrete mucus, to lubricate the food in the act
of deglutition.
869. The instruments of taste are the two other sets of papillae. One
set consists of small, oval-shaped bodies, which are scattered over
the whole surface of the tongue. They give it a rough appearance, and
are called the _fil'i-form_ papillae.
870. The other set of papillae is called the _fun'gi-form_. They are
larger than the former, and consist of small, rounded heads, supported
on short stalks, something in the shape of mushrooms, from which they
derive their name. In the last two described sets of sensitive
papillae, the gustatory branch of the fifth pair of nerves ramifies.
_Observation._ By applying strong acids, as vinegar, to the tongue,
with a hair pencil, these points will become curiously lengthened.
PHYSIOLOGY OF THE ORGANS OF TASTE.
871. TASTE is the sense which makes us acquainted with the savor of
substances. When fluids are taken into the mouth, the papillae dilate
and erect themselves, and the particular impression excited is
transmitted to the brain through filaments of the gustatory nerve.
This sense is closely connected with that of smell. The pleasures
derived from it are strictly sensual and corporeal, and contribute in
no way to the expansion of the mind, like those of hearing and
seeing.
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How many varieties of papillae? Describe the first variety. What is the
function of the lenticular papillae? 869. Describe the filiform
papillae. 870. The fungiform papillae? What nerve ramifies in the
fungiform papillae? How can these papillae, or points, be seen? 871-875.
_Give the physiology of the organs of taste._ 871. Define taste.
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872. If dry, solid food is taken, the tongue carries it to the back
side of the mouth, where it receives secretions from the salivary
glands; the saliva, becoming impregnated with its flavor, flows over
the sides of the tongue, and gives to the papillae a perception of the
savory juice; this impression is then communicated to the brain.
_Observation._ It is supposed that the salts which enter into the
composition of the saliva, are very efficient agents in reducing
substances to a proper state for making impressions on the nerves of
taste. The fact that metals impart a peculiar taste, is owing to a
galvanic shock, and not properly to what we understand by taste.
873. The primary use of taste is to guide animals in the selection of
food, and to warn them against the introduction of noxious articles
into the stomach. In all the inferior animals, we see that the
original design of taste is still answered. But in man, this sense has
been so abused and perverted, by the introduction of stimulants and
condiments, and the endless admixture of different articles of food,
that the simple action of this part seems to have been superseded
almost entirely by acquired taste.
874. In children, this sense is usually acute, and their preference is
for food of the mildest character. And it is also true, that every
person has some peculiarities of taste, or dislikes to particular
articles of food. This may be either constitutional or from the
influence of association.
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With what sense is this closely connected? What is said of this sense?
872. Give the process by which we taste substances. How can we account
for the taste of metals when applied to the tongue? 873. What is the
primary use of taste? Where do we see it perverted? 874. How is this
sense in children? What is true of every person in reference to
taste?
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_Observation._ This sense has been made to vary more than any other by
the refinements of social life. Thus, the Indian's like or dislike to
particular kinds of food, generally extends to every person of the
same tribe; but among civilized men, no two individuals can be found
alike in all their tastes.
875. This sense is modified by habit, and not unfrequently those
articles, which at first were disgusting, become highly agreeable by
persevering in the use of them. By cultivation, this sense may be made
very acute. Those persons whose business leads them to judge of the
quality of an article by their taste, can discriminate shades of
flavor not perceivable by ordinary persons. Epicures, and tasters of
wines and teas, afford examples.
_Observation._ Many persons impair their taste by bad habits, as
chewing and smoking tobacco, and using stimulating drinks, and pungent
condiments with the food. These indulgences lessen the sensibility of
the nerve, and destroy the natural relish for food.
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What is true of the Indian? 875. Is this sense modified by habit? Give
instances. How is this sense sometimes impaired?
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