The tastes of plants conduct us more certainly to their medical properties; but the similarity of terms may contribute, without care, to confound them with the smells. Our chief guide in this path is Linnaeus himself; but Bergius, assisted by the comprehensive Linnaean language, has greatly extended our distinctions of taste; though employing terms and comparisons generally known, he scarcely requires an interpreter. Taste has been considered as a cause of the action of medicines, or at least as a means of discovering their properties in almost every era of medicine since that of Hippocrates; and,besides Linnaeus, Wedelius, Walther, Hebenstreit, Koenig, and Tauvry, have paid particular attention to it. The two last have, however, confined themselves to mechanical explanations of taste; and, like Willis, have supposed acrid particles needles, oily ones spheres; bitter, salt, acid, and styptic tastes, owing to forked, irregular, polyedral, conical, or hooked particles respectively.

Tastes greatly differ; and though, as in smells, we say in general that substances of an agreeable taste are salutary, and those which are unpleasing to the palate injurious, yet the question of pleasantness or its opposite is relative. Pungent tastes are universally painful; but, when diluted, they become agreeable. In fact, as we shall find in the operation of medicines, every thing in excess is stimulant: we only perceive either peculiar properties, or flavours, when the proportion is suitable to the circumstances. Fourcroy divides tastes into those which are highly pungent or painful, as the caustics; those which excite moderate sensation, as the sweets and bitters; such as only affect the stomach, and very slightly, if at all, the palate, as the antimonials; and such as act only through the medium of the nerves. We need not add that this is to extend the subject beyond its proper limits. It is singular, that the people on the coast of Malabar, among whom medicine is in a very rude slate, divide their remedies according to taste. Grundler, the Danish missionary who visited that country in the beginning of the last century, has given an extract from the Voya da-satyram, which contains all their medical science, where the remedies are divided into acids, sweets, bitters, acrids, and astringents. We may just add, that Braun, the son-in-law of Haller, an officer in our service in Indostan, has informed us, that, in the ancient seminary of Benares, no other part of medicine is cultivated except what relates to the virtues of vegetables; and in the Gottingen museum, a valuable hortus siccus of Malabar plants in twelve volumes folio, with their names and properties annexed, was some time since preserved.

Linnaeus divides the taste of medicines (Amoenitates Academicae, ii. 335) into the sweet and acrid; the fat and styptic; the acid and bitter; the viscid and salt: the watery and dry. The styptic is a compound taste, sometimes consisting of the dry and acid, when it is styled austere; or of the dry and bitter, distinguished by the term acerb. The nauseous taste produces an inverted motion of the oesophagus and stomach. It is a compound, but its ingredients are not easily ascertained. We are informed by Quercetanus, that the medicines styled by Hippocrates bitter, acid, and sweet, are. by Galen, in conformity to his theory of the humours, called hot and cold, wet and dry.

The property of sweetness is conspicuous in the roots of the polypody and liquorice; all ripe fruits; in milk and in honey. The sweets, either saccharine or mucilaginous (vide manna) are, as we have seen, nutritious, chiefly adapted to dry, lean habits, and advanced life. They are also demulcent, and supposed to be expectorant; but the latter quality rests on a doubtful foundation.

Medicines distinguished by an acrid taste are heating, irritating, and, in excess, corrosive. In large doses they are the most destructive poisons. Externally, they are rubefacient, sometimes discutient, or occasionally suppurative. By their general stimulus they promote every evacuation, and are sometimes the most active emetics. Their powers as cathartics are less conspicuous, and they are generally useful in cold, phlegmatic habits. Examples of this kind are the pure alkalis, and the metallic salts; the roots of bryony, pyrethrum, horse radish, and of the alliaceous tribe; the leaves of the soldanella, persicaria, tithymalus and cochlearia; the bark of the elder; the seeds of the mustard; eu-phorbium, gamboge, and cantharides.

The fat taste is conspicuous in the almond, cocoa nut, lintseed, and axunge. It is owing to an oil combined with a mucilage, and is lost when they become rancid. They are in general demulcent, and useful when the fibres are stretched, or the mucous membranes abraded. From this last circumstance, they sometimes relieve diarrhoeas, though many of this class are naturally-laxative.

The contraction of the mouth, which arises from tasting styptics, is sometimes communicated to other parts. Alum is a striking example; but it does not follow that styptic vegetables, as has been supposed, contain an argillaceous sulphat. We find this taste in variolated iron and zinc; the roots of tormentil, bistort, and quinquefolium; the barks of the tamarisk, the capparis, and the fraxinus; the gall nut; the leaves of the centinodium, the myrtle, and the oak; the flowers of pomegranate, and in red roses; the juice of acacia, catechu, etc. These remedies are, in general, astringent; and, as they all contain tanin in a considerable proportion, we find the foundation of their properties in the separation of the gelatin. See Astringentia.

Of the acid taste we require no examples; but if we speak of this as a natural one, we must exclude the mineral acids, which rather belong to the styptics. With this exception, we shall find acid substances cooling and sedative, neutralizing in some degree the bile, and destroying putrid acrimony in the stomach. They allay thirst, promote a discharge from the kidneys, and often from the skin. They prevent accumulations of fat in the cellular membrane; but do not, as has been said, coagulate the fluids; for they do not reach the circulating system with their properties unchanged.