The system of Linnæus, although in a great degree artificial, corresponds in a surprising manner with the natural properties of plants; thus a plant whose calyx is a double valved glume, with three stamina, two pistils, and one naked seed, bears seeds of a farinaceous and nutritious quality; a flower with twelve, or more stamina, all of which are inserted in the internal side of the calyx, will furnish a wholesome fruit; whereas a plant whose flower has five stamina, one pistil, one petal, and whose fruit is of the berry kind, may at once be pronounced as poisonous.
It is also in a great degree true that the sensible qualities of plants, such as colour, taste, and smell, have an intimate relation to their properties, and may often lead by analogy to an indication of their powers; we have an example of this in the dark and gloomy aspect of the Luridæ, which is indicative of their narcotic and very dangerous qualities, as Datura, Hyoscyamus, Atropa, and Nicotiana. Colour is certainly in many cases a test of activity; the deepest coloured flowers of the Digitalis, for example, are the most active, and when the leaves of powerful plants lose their green hue, we may conclude that a corresponding deterioration has taken place with respect to their virtues; but Linnæus ascribed too much importance to such an indication, and his aphorisms are unsupported by facts; for instance, he says “Color pallidus insipidum, viridis crudum, luteus amarum, ruber acidum, albus dulce, niger ingratum, indicat.”[[87]] A peculiar heavy odour, which is well known, but is with difficulty defined, is a sure indication of narcotic properties. Bitterness, when not extreme, denotes a tonic quality, which will stimulate the stomach and intestines, and promote the process of digestion. When the bitterness is more intense and pungent,[[88]] as in Aloes, Colocynth, &c. we may infer that such substances will produce a more active effect upon the primæ viæ, and that catharsis will follow their administration.
Botanical, like human physiognomy, may frequently afford an insight into character, but it is very often a fallacious index. With regard to the indications of Smell and Taste, it may be observed that in the examination of an unknown substance we instinctively apply to these senses for information respecting its properties. It is certainly reasonable to suppose, that those bodies which produce upon the organs of taste a sensible, astringent, or pungent effect, may occasion an impression, corresponding in degree upon the stomach or intestines, which are but an extension of the same structure. But what numerous exceptions are there to such a law? nay, some of the most poisonous substances affect in a very slight degree the organs of taste, especially those that belong to the mineral kingdom, as Arsenious Acid, Oxyd of Antimony, Calomel, &c.; yet some of these are, perhaps, but apparent exceptions, depending upon the degree of solubility which they possess, in consequence of which their energies are not developed until they have traversed a considerable portion of mucous surface. Nor ought it to be forgotten, that cultivation and artificial habits may have blunted the natural susceptibility of our organs, and in some instances changed and depraved their functions: certain qualities for instance are so strongly connected with each other by the chain of association, that by presenting only one to the mind, the other links follow in succession.[[89]] It has been remarked, that persons in social life, are more affected by vegetable odours, while the Savage smells better the putrid and fœtid exhalations of animal bodies:[[90]] thus the people of Kamskatcha, did not smell the perfume of a vegetable Essence (Aqua Melissæ,) but they discovered by their olfactory sense, a rotten fish, or a stranded whale at a considerable distance.[[91]] There is no sense more under the dominion of imagination, or more liable to be perverted by education, than those of taste and smell; we are also liable to form unjust prejudices from the indications of colour; for particular colours, from the influence of hidden associations, are not unfrequently the exciting cause of agreeable or unpleasant impressions. I have met with a person who regards green food, if it be of an animal nature, with unconquerable aversion and disgust, indeed an idea of unwholesomeness has not unfrequently been attached to this colour, without the least foundation of truth; the bones of the Gar fish, or Sea Needle, (Esox Helone,) have been deemed unwholesome from the circumstance of their turning green on being boiled, although not a single instance can be adduced in which that fish ever occasioned any harm. I have met with persons who have been made violently sick from eating the green part of the oyster;[[92]] an effect which can have no other cause than that of unjust prejudice; these examples are sufficient to shew, with what caution such indications respecting the medicinal qualities of bodies are to be received.
THE APPLICATION AND MISAPPLICATION OF CHEMICAL SCIENCE.
Amongst the researches of different authors, who, animated with a sacred zeal for ancient learning, have endeavoured to establish the antiquity of chemical science, we find many conclusions deduced from an ingenious interpretation of the mythological fables[[93]] which are supposed to have been transmitted by the Egyptians; who, previous to the invention of letters, adopted this method of perpetuating their discoveries in natural philosophy. Thus, wherever Homer studiously describes the stolen embraces of Mars and Venus, they recognise some chemical secret, some combination of iron with copper, shadowed in the glowing ornaments of fiction. Lord Bacon[[94]] conceived that the union of spirit and matter was allegorised in the fable of Proserpine being seized by Pluto as she was gathering flowers; an allusion, says Dr. Darwin, which is rendered more curiously exact by the late discovery, that pure air, (oxygen) is given out by vegetables, and that in this state it is greedily absorbed by inflammable bodies. The same ingenious Poet supposes that the fable of Jupiter and Juno, by whose union the vernal showers were said to be produced, was meant to pourtray the production of water by the combination of its two elements; an opinion which, says he, is strongly supported by the fact that, in the ancient mythology, the purer air or æther, was always represented by Jupiter, and the inferior by Juno. Were the elegant author of the Botanic Garden now living, he would, no doubt, with a taste and delicacy peculiarly his own, avail himself of the singular discovery of Mr. Smithson, who has detected in the juice of the mulberry two distinct species of colouring matter;—the mingled blood of the unfortunate Pyramus and Thisbe:
“Signa tene cædis: pullosque et luctibus aptos
Semper habe feætus, gemina monumenta cruoris.”
Ovid. Metamorph. Lib. iv. 160.
Sir William Drummond, the learned apologist of Egyptian science, conceives that the laws of latent heat were even known to the philosophers of that ancient nation, and that caloric in such a state, was symbolically represented by Vulcan, while free or sensible caloric was as clearly described in the character of Vesta. Those who maintain the antiquity of chemistry, and suppose that the fabulous conceptions of the ancients were but a mysterious veil ingeniously thrown by philosophy between nature and the lower order of people, consider that the alchemical secret is metaphorically concealed in the fable of the Golden Fleece of the Argonauts, and reject the more probable solution of this story by Strabo, who says that the Iberians, near neighbours of the Colchians, used to receive the gold, brought down from the high lands by the torrents, into sieves and sheep skins, and that from thence arose the fable of the golden fleece. Dionysius, of Mytilene, offers a different explanation of the fable, and supposes it to allude to a book written on skins, and containing an account of the process of making gold according to the art of alchemy.
Notwithstanding the confidence with which modern philosophers have claimed the discovery, the experimental mode of investigation was undoubtedly known and pursued by the ancients, who appear, says Mr. Leslie,[[95]] to have concealed their notions respecting it, under the veil of allegory. Proteus signified the mutable and changing forms of material objects, and the inquisitive philosopher was counselled by the Poets[[96]] to watch their slippery demon when slumbering on the shore, to bind him, and compel the reluctant captive to reveal his secrets. This, adds Mr. Leslie, gives a lively picture of the cautious, but intrepid advances of the skilful experimenter;—he tries to press nature into a corner,—he endeavours to separate the different principles of action,—he seeks to concentrate the predominant agent, and labours to exclude, as much as possible, every disturbing influence.