See also:analogy, the word " taste " is used also of aesthetic appreciation (see
See also:AESTHETICS) and a sense of beauty—commonly with the qualifications "
See also:good taste " and "
See also:bad taste." The physiological sense is located almost entirely in the
See also:tongue . Three distinct sensations are referable to the tongue—(1) taste, (2)
See also:touch, and (3) temperature . The posterior
See also:part of its
See also:surface, where there is a A-shaped
See also:group of large papillae, called circumvallate papillae, supplied by the glosso-pharyngeal nerve, and the tip and margins of the tongue, covered with filiform (touch) papillae and fungiform papillae, are the chief localities where taste is manifested, but it also exists in theglosso-palatine arch and the lateral part of the soft palate . The
See also:middle of the tongue and the surface of the hard palate are devoid of taste . The terminal
See also:organs of taste consist of
See also:peculiar bodies named taste-bulbs or taste-goblets, discovered by Schwalbe and S . L . Loven in 1867 . They can be most easily demonstrated in the papillae foliatae, large
See also:oval prominences found on each side near the
See also:base of the tongue in the
See also:rabbit . Each papilla consists of a series of laminae or folds, in the sides of which the taste-bodies are readily displayed in a transverse section . Taste-bodies are also found on the lateral aspects of the circumvallate papillae (see Fig . 1), in the fungiform papillae, in the papillae of the soft palate and uvula, the under surface of the epiglottis, the upper part of the posterior surface of the epiglottis; the inner sides of the
See also:arytenoid cartilages, and even in the vocal cords .
The taste-bulbs areminute oval bodies, somewhat like an old-fashioned Florence
See also:flask, about soa inch in length by sh in breadth . Each consists of two sets of cells—an
See also:outer set, nucleated, fusiform, bent like the staves of a
See also:barrel, and arranged side by side so as to leave a small opening at the
See also:apex (the mouth of the barrel), called the gustatory
See also:pore; and an inner set, five to ten in number, lying in the centre, pointed at the end next the gustatory pore, and branched at the other extremity . The branched ends are continuous with non-medullated nerve
See also:fibres from the gustatory nerve . These taste-bodies are found in immense numbers: as many as 176o have been counted on one circumvallate papilla in the ox . The proofs that these are the terminal organs of taste
See also:rest on careful observations which have shown (I) that taste is only experienced when the sapid substance is allowed to come into contact with the taste-
See also:body, and that the sense is absent or much weakened in those areas of mucous membrane where these are deficient; (2) that they are most abundant where the sense is most acute; and (3) that section of the glosso-pharyngeal nerve which is known to be distributed to the areas of mucous membrane where taste is
See also:present is followed by degeneration of the taste-bodies . At the same
See also:time it cannot be asserted that they are absolutely essential to taste, as we can hardly suppose that those animals which have no
See also:special taste-bodies are devoid of the sense . Evidence is accumulating that taste depends on
See also:nervous impulses excited by chemical
See also:change . Substances that haves taste must be soluble . Chemical changes are in all probability set up in the taste-cells, or in the processes connected with them . Some progress has been made in the attempt to establish a d' connexion between the chemical composition of sapid substances and the different kinds of taste to which they may give rise . Thus acids are usually sour; alkaloids have a peculiar soapy taste; salts may be sweet, like
See also:sugar of lead, or bitter, like sulphate of
See also:magnesia; soluble alkaloids, such as
See also:quinine or
See also:strychnine, are usually bitter; and the higher alcohols are more or less sweet . Substances which taste sweet or bitter often contain definite groups in the molecule, especially in the hydroxyl (HO) and amido (
See also:NH2) groups .
By altering the I chemical composition of a substance having a characteristic taste (changing the position or relations of the radicles), the substance may become tasteless or intensely bitter . The sensation of taste may also be excited mechanically, as by smartly tapping the tongue, or by the stimulus of a continuous current . In the lattercase electrolytic change may be the exciting cause; but that the sense organs may be stimulated electrically is proved by the fact that rapidly interrupted induced currents, which produce little or no electrolysis, may also excite taste . Sensations of taste are heightened by increasing the
See also:area of the tongue affected, and by
See also:mechanical stimulation, as when the tongue is pressed against the lips, cheeks or palate . A temperature of about 40° C. is most favourable, either extreme
See also:heat or
See also:cold apparently benumbing the sense for a time . Gustatory sensations affect each other: that is to say, a strong taste will affect the taste of another body taken immediately after it . Thus sweetness will modify bitterness, and sourness will modify both . Moreover, the application of a sapid sub-stance to the tongue will affect taste in other parts . If the same taste is excited on each side of the tongue, although there are two sets of gustatory nerves, one for each lateral
See also:half, the sensations are blended into one; while if two different sub-stances, say one sweet and the other bitter, are simultaneously applied, one to each side, the observer can distinctly differentiate the one from the other . Tastes have been variously classified . One of the most useful classifications is into sweet, bitter, acid and saline tastes . Insoluble substances, when brought into contact with the tongue, give rise to feelings of touch or of temperature, but excite no taste .
If solutions of various substances are gradually diluted with
See also:water until no taste is experienced, G . G . Valentin found that the sensations of taste disappeared in the following order—syrup, sugar,
See also:salt, aloes, quinine, sulphuric acid; and Camerer found that the taste of quinine still continued although diluted with twenty times more water than common salt . The time required to excite taste after the sapid substance was placed on the tongue varies . Thus saline matters are tasted most rapidly (•17 second), then sweet, acid and bitter (.258 second) . There are many curious examples of substances of very different chemical constitutions having similar tastes . For example, sugar, acetate of lead and the vapour of
See also:chloroform have all a sweetish taste . A temperature of from 50° to 90° F. is the most favourable to the sense, water above or below this temperature either masking or temporarily paralysing it . As a general
See also:rule, bitter tastes are most acute at the back of the tongue, near the circumvallate papillae, and sweet tastes at the tip, but there are considerable individual variations . Some persons taste both bitter and sweet substances best at the back, while others taste bitter things at the tip . Many experience salt tastes best at the tip, and acid tastes at the sides of the tongue . When we consider that there are three kinds of papillae on the surface of the tongue, one would expect to meet with different degrees of sensitiveness to different tastes, even while we admit that the papillae may also have to do with sensations of touch and of temperature .
By experimenting with
See also:fine capillary tubes containing sapid substances, observations have been made with individual papillae . Some are found to be sensitive to many tastes, others to two or three, others to only one, while others are insensitive to taste altogether . Again, it has been found that a mixture of sapid substances, say of quinine and sugar, may taste sweet when applied to one papilla end bitter when applied to another . The inference must bethat there are special terminal organs for different tastes . Assuming that there are different kinds of taste-cells, it might be possible to paralyse some without affecting others, and thus different sensations of taste might be discriminated . This has been done by the use of the leaves of a common
See also:Indian plant, Gymnema sylvestre . If some of these be chewed, it has been found that
See also:bitters and sweets are paralysed (neither quinine nor sugar giving rise to sensation), while acids and salines are unaffected . Again, certain strengths of decoctions of the leaves appear to paralyse sweets sooner than bitters . These observations show the existence of different taste-cells for sweets, bitters, acids and salines; and it is clear that the region of the tongue most richly supplied with taste-cells sensitive to sweets will
See also:respond best to sweet substances, while another region, supplied by taste-cells sensitive to bitters, will respond best to bitter substances . In like manner the
See also:argument may be applied to other tastes . Suppose, again, a set of taste-cells sensitive to bitter substances: it is conceivable that in whatever way these were irritated, a bitter taste would result . If so, a substance which, applied to one part of the tongue, would cause a sweet sensation, might cause a bitter if applied to a part of the tongue richly supplied with taste-cells sensitive to bitters .
This may explain why sulphate of magnesia excites at the
See also:root of the tongue a bitter taste, while applied to the tip it causes a sweet or an acid taste . Saccharine, a peculiar
See also:toluene derivative, in like manner is sweet to the tip and bitter to the back of the tongue . It has also been found that if the sweet and bitter taste-cells are paralysed by Gymnema, electrical irritation of the tip by a weak interrupted current does not give rise to an acid taste mixed with sweet, as it usually does, but to sensations somewhat different, which may be described as metallic or salt or acid . This experiment indicates that the
See also:action of the interrupted current on the terminal
See also:organ is analogous to the action of sweet or bitter substances (
See also:Shore) . No
See also:direct observations of importance have yet been made on single circumvallate papillae . Further experiments with capillary tubes show that fungiform papillae destitute of taste buds, and areas of the surface of the tongue having neither papillae nor taste buds, may still, when stimulated by sapid substances, give rise to tastes . Taste is often associated with smell (q.v.), giving rise to a sensation of flavour, and we are frequently in the
See also:habit of confounding the one sensation with the other . Chloroform excites taste alone, whilst
See also:garlic, asafoetida and
See also:vanilla excite only smell . This is illustrated by the
See also:familiar experiment of blindfolding a
See also:person and touching the tongue successively with slices of an
See also:apple and of an
See also:onion . In these circumstances the one cannot be distinguished from the other when the
See also:nose is firmly closed . Taste may be educated to a remarkable extent; and careful observation—along with the practice of avoiding all substances having a very pronounced taste or having an irritating effect—enables
See also:tea-tasters and
See also:wine-tasters to detect slight differences of taste, more especially when combined with odour so as to produce flavour, which would be quite inappreciable to an ordinary palate . As to the action of electrical currents on taste, observers have arrived at uncertain results .
Solong ago as 1752 J . G . Sulzer stated that a
See also:constant current caused, more especially at the moments of opening and of closing the current, a sensation of acidity at the anode (+
See also:pole) and of alkalinity at the katode (—pole) . This is in all probability due to electrolysis, the decomposition products exciting the taste-bodies . Rapidly interrupted currents fail to excite the sense . Disease of the tongue causing unnatural dryness may interfere with taste . Substances circulating in the
See also:blood may give rise to subjective sensations of taste . Thus santonine, morphia and biliary products (as in
See also:jaundice) usually cause a bitter sensation, whilst the sufferer from diabetes is distressed by a persistent sweetish taste . The insane frequently have subjective tastes, which are real to the patient, and frequently cause much
See also:distress . In such cases, the sensation is excited by changes in the taste-centres of the
See also:brain . Increase in the sense of taste is called hypegeusia, diminution of it hypogeusia, and its entire loss ageusia . Rare cases occur where there is a subjective taste not associated with insanity nor with the circulation of any known sweetish matters in the blood, possibly caused by irritation of the gustatory nerves or by changes in the nerve centres .
For theanatomy of the organs of taste, see the articles MOUTH and TONGUE . (J . G .
ALESSANDRO TASSONI (1565-1635)
JAMSETJI NASARWANJI TATA (1839-1904)
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