2

ELEMENTS OF MATERIA MEDICA.

quinia), which agree in these properties, disagree in the effects whichthey produce on the organism.

The natural-historical properties (external form and structure) are oflittle value in ascertaining the operation of either mineral or animal sub-stances. It is well known that two dissimilar bodies may assume thesame crystalline shape, and they are said, therefore, to be isomorphous.Identity of form in the mineral kingdom depends not on the quality, buton the number, of the constituent molecules.

No attempts have been made to trace any relation between the toxicolo-gical or edible properties and the anatomical structure of animals. Thishas probably arisen from the comparatively small number of these beingswhich possess medicinal or poisonous properties; for we are enabledto employ, as food, animals of every class, from the highest to the lowest.Among quadrupeds and birds no species is poisonous, unless, indeed, theArctic bear be an exception, whose liver is stated by Captain Scoresbyto be deleterious. — ( Fleming’s Philosophy of Zoology, vol. ii. p. 110.)Among fishes, molluscous animals, and insects, however, several speciesare hurtful; and it is frequently found that where one is deleterious,kindred species are likewise more or less so. Thus all the coleopterousinsects belonging to the tribe Cant har idiot (Latreille) possess blisteringproperties.

The relations existing between natural-historical qualities and medici-nal effects have been attentively examined with respect to vegetables. Ithas long been supposed that those plants which resemble each otherin their external appearances arc endowed with analogous medicinalproperties. Cicsalpinus was, according to Dierbach, the founder ofthis doctrine; though Decandolle regards Camerarius as the first whoclearly announced it. Linnaeus says, “ Plantse qua; genere conveniunt,etiam virtute conveniunt; qua) ordine naturali continental', etiam virtutepropius accedunt; quaeque classe naturali congruunt, etiam viribusquodammodo congruunt.”—( Philosophia Botanica, ed. 4ta. p. 278.) Imay also refer to Isenflamm, Wilcke, Gmelin, Jussieu, and Barton, asother supporters of this opinion. But the most important writer in favourof it is Decandolle, who, in 1804, published his Essai sur les ProprietesMedicates des Plantes; a second edition of which appeared in 1816. Inthe year 1831, we had another interesting treatise on the same subject byDierbach . ( Abhandlung iiber die Arzneikrdfte des Planzen, vergleichenmit Hirer Structur und ihren chemischen Bestandtheilen.) There areother writers, however, who deny altogether the possibility of judging ofthe virtues of plants by their exterior forms and botanical characters. Ofthese I shall refer to one only, namely, Gleditsch (Be Methodo botanicadubio et fallaci virtutum in plantis indice, 1742.)

It must be admitted that vegetable substances owe their pecidiar quali-ties to the structure and consequent action of the organs producing them;and, therefore, that alterations in the structure of an organ, are attendedwith corresponding alterations in the qualities of its products. It conse-quently follows that the medicinal qualities of plants should accord withtheir classification in natural families. That they do so to a certain ex-tent is fully ascertained by numerous facts. If one vegetable speciesserve as nutriment for either animal or plant, we frequently observe thatother species of the same genus, or even of a different genus but of thesame family, are also adapted for a like use; while, on the other hand, if