Muscles of the Tongue.—The muscles of the tongue are usually divided into two groups—viz.: the extrinsic muscles, which attach the tongue to certain fixed points external to it, and move it on them; and the intrinsic muscles, which pass from one part of the tongue to another, constitute its chief bulk, and move it on itself. These intrinsic muscular fibers run vertically, transversely, and longitudinally, and are so interlaced as mutually to support one another, and to act with the greatest advantage.
The Bulbs of Taste.—The mucous membrane is invested by stratified cells, which, over the surface of the tongue, cover little vascular projections termed, papillæ. At the back of the tongue are some eight or ten papillæ of quite a different nature, called “circumvallate.” They are arranged to form a V with its angle pointing backward. In the epithelium lining the trenches between the papillæ, curious little bodies called taste-bulbs are lodged. Each taste-bulb looks like a flask-shaped barrel or box, the walls of which are composed of flat elongated cells fitted side by side like the staves of a cask. The taste-bulbs open each by a little pore into the trench, and into the deeper part a nerve enters. The impressions are carried by the nerve directly to the brain in either the fifth or the ninth cranial nerves.
Before the substance can stimulate the terminals it is necessary for its aromatic principles to be in solution. This is generally effected through the agency of the saliva.
Four distinct gustatory qualities are appreciated by the sense of taste—sweetness, bitterness, acidity, and salinity. The intensity of the sensation of taste varies with (1) the area of the surface stimulated, (2) the concentration of the stimulant, (3) the length of the period of application, and (4) the temperature of the substance tasted. Tractile impressions, such as harshness, coolness, and astringency, are erroneously attributed to taste.
Mis-Educated and Educated Taste.—Of all the organs of the senses, that of taste is probably the one which receives the worst usage at our hands. The eye, the ear, and the nose are not educated at all, or their education is left to chance, but the tongue is deliberately mis-educated, perverted, and led astray. We eat what we should not eat; drink what we should not drink: eat too much of what we may eat, and drink too much of what we may drink. And the result is, that we ruin our health, enfeeble our bodies, dull our intellects, brutalize our feelings, and harden our hearts.
Yet assuredly taste has its legitimate domain, and it is as unworthy of man’s true dignity that he should be content to live upon the husks that the swine do eat, as that he should be miserable if he do not fare sumptuously every day. All the other senses have a direct interest in the practical decisions of the sense of taste. Drunkenness and dyspepsia dim the eye, dull the ear, blunt the nostril, and make the hand tremble.
A Victim to the Other Senses.—The sense of taste, in truth, is at the mercy of the other senses; and though it can revenge itself for their neglect or misuse of it, it is a sufferer by its own revenge.
Helpless, selfish, and exacting, the dependent of the other senses, and the servant of the body rather than of the soul, it frequently links us more with the lower animals than with higher existences, and has no element of ethereality about it.
A feast, indeed, may furnish pleasure to every sense, but it is usually not till hunger is appeased that the higher senses are ministered to. But the tongue, as the organ of taste, is the commissary-general, without whose supplies the other senses can achieve no conquests, and it is entitled to its share in the honors assigned to the united five; but its own sword is seldom drawn, and its aspect is not heroic.