TASTE

Categories: Diseases of The Nervous System

Taste-Buds. There are three kinds of papillae or eminences on the
human tongue,--the circumvallate, the fungiform and the filiform. The

circumvallate are from seven to twelve in number and lie near the root of

the tongue, arranged in the form of a V, with its open angle turned

forward. Each one is an elevation of the mucous membrane, covered by

epithelium and surrounded by a trench. On the sides of the papillae,

embedded in t e epithelium, are small oval bodies called taste-buds. These

taste-buds consist of a sheath of flattened, fusiform cells, enclosing a

number of spindle-like cells whose tapering ends are prolonged into a

hair-like process. As the filaments of the gustatory nerves terminate

between these rod-like cells, it is probable that they are the true

sensory cells of taste.






In the human tongue taste-buds are also found in the fungiform papillae,

often seem as red dots scattered over its surface; and to an area just in

front of the anterior pillar of the fauces. It is also possible that

single taste-cells are scattered over the tongue, as the sense of taste

exists where no taste-buds can be found.






Many so-called tastes are really smells. This is easily proved by

compressing the nostrils and attempting to distinguish by taste different

articles of food.



The taste sensation is greatest when the exciting substance is at the

temperature of the body. There is no perceptible sweetness to sugar when

the tongue has been dipped for a half-minute in water either at the

freezing temperature or warmed to 50 degrees C. Neither is there any sense

of taste until the substance is dissolved by the natural fluids of the

mouth, as will be seen by wiping the tongue dry and placing sugar upon it.



The four primary taste-sensations are bitter, sweet, sour and salt. These

probably have separate centers and nerve fibers. Sweet and sour tastes are

chiefly recognized at the front and bitter and alkaline tastes at the back

of the tongue. The same substance will often excite a different sensation,

according as it is placed at the front or back of the tongue.



There are also laws of contrast in taste sensations. Certain substances

will enhance the flavor of another and others will destroy it. Again,

certain tastes may disguise others without destroying them, as when an

acid is covered with a sweet.