Tongue

tung, in human physiology, a muscular organ placed in the floor of the mouth between the two branches of the lower jaw. With the exception of a few frog-like animals and some birds, the tongue belongs to all vertebrate animals. In some it is much more movable than in others. The tongue of the lion and of the snail is furnished with rough points, enabling it to be used as a rasp. The tongue of the woodpecker and of the chameleon is pointed with a barb, enabling it to transfix insects. The tongue of serpents is forked. The giraffe has a long, flexible tongue with which it is able to draw leaves and twigs into its mouth. The cat and dog are capable of shaping the tongue into a sort of cup, with which to lap water. The anteater of South America has a mouth about half an inch in diameter. It has a long, slender tongue which it can thrust out about nine inches.

The human tongue is used in speaking, licking, chewing, swallowing, and in spitting. The upper surface is paved like the Giant's Causeway, with the upturned ends of numerous nerves. The end of the finger is able, for instance, to distinguish between a solid and a liquid, a warm substance and one that is cold, an oily surface from one that is rough, etc., but the nerves of the tongue are able to do more. They can distinguish between sweet, sour, bitter, and salt, as well as detect the peculiar flavor of a thousand different articles of food. This special power is called the sense of taste. It is the special province of these nerves to taste the food that enters the mouth and to guard the stomach from poisonous or offensive diet. Each part of the sensitive upper surface of the tongue seems to have its special work to do. The nerves that detect sugar are not affected by spice. The nerves that detect a bitter taste do not detect salt. The nerves that detect sweets are situated on the fore part of the tongue, those that detect sour, farther back. In eating candy, for instance, it is natural to drop the head forward, so that the piece will fall on the front of the tongue. In tasting vinegar, it is natural to toss the head up, thus bringing the vinegar on the back part of the tongue. Sugar cannot be tasted immediately after hot soup or ice-water. Bitter is distinguished more readily than sweet or sour. One part of quinine can be detected in 1,000,000 parts of water.

In his Education of the Central Nervous System, Hallock suggests that the sense of taste can be cultivated by discriminating between such flavors as strawberry, grape, apple, pea, peach, orange, lemon, quince, blackberry, cherry, pineapple, banana, raspberry, currant, gooseberry, cranberry, citron, plum, raisin, vanilla, wintergreen, peppermint, spearmint, sassafras, catnip, fennel, caraway, sage, cinnamon, clove, nutmeg, rhubarb, ginger, honey, sugar, and salt, as well as the different meats and drinks. An expert tea taster in the employ of a large tea importing house learns to discriminate between the different grades of tea to a nicety. The tongue of the professional wine taster becomes as sensitive to flavor as does the ear of a musician to sound. The nearest counterpart to the nerves of taste are the nerves of smell. They are even more delicate and more highly specialized.