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sophers have distinguished by the name of adhesion has some properties in common with chemical attraction, such as the point of saturation, and elective affinity, and that hence it appeared to me, to be very properly termed attraction of

surfaces.

I shall not hesitate however, to renounce the principle I' have adopted, that of an attraction of surfaces, and retract' the explanations of some interesting phenomena, which I have deduced from this principle, and given in the papers already mentioned, if convincing facts and just reasonings show me their incompetency.

V.

Abstract of an Essay on the Medicinal Properties of Plants compared with their external Form and natural Classifications: by Mr. DECANDOLLE*.

No branch of study deserves the name of science, till it Indication of

the virtues of

drugs.

is sufficiently advanced, to be able to determine facts a priori. The materia medica, which rests entirely on the basis of ex perience, has but three means of forming a judgment of the properties of substances; which are, their sensible qualities," their chemical composition, and their natural analogy. The object of Mr. Decandolle's work, which forms a quarto volume, is to ascertain how far the analogy of the forms of vegetables affords indications of their properties. Camerarius first decidedly took up the affirmative side of Have plants sithis question in 1699. He was followed by Isenflamm, pearance simi Wilka, Gmelin, and more especially by Linneus and de Jus- lar virtues? sieu. On the other hand Vogel, Plaz, and Gleditsch wrote against it. Notwithstanding what has been written by these learned men, Mr. Decandolle has contrived to treat the question with some novelty, not only in consequence of the progress, that the study of natural affinities has made within these twenty or thirty years; but because, confining himself exclusively to no system, he has formed his deductions not from

Annales de Chimie, Vol. LXI, p. 84, January, 1807.

VOL. XIX.-JAN. 1808.

C

a few

milar in ap

Arguments for

it.

Observations

Arm it.

a few solitary families, but from all that compose the vegetable kingdom.

He commences with establishing the general proofs, that the medicinal properties of plants are analogous to their external forms. In fact no one will question, that the properties of medicines depend on their physical constitution or chemical composition: but in organized bodies the nature of a production is determined by the form of the organs, since the same aliments, digested by different beings, afford different results; consequently the productions bear some relation to the forms. This reasoning is applicable to the vegetable kingdom, though its classification is not derived from the organs of nutrition, but from those of reproduction; for the natural classes deduced from one function necessarily agree with those deduced from another function.

These general inferences are confirmed by the observation, tending to con- that herbivorous animals frequently avoid or seek all the plants of the same family: that those, which seem determined to feed ouly on a single plant, frequently submit to eat plants of the same genus, or of the same family: and that parasitic plants, particularly funguses, display the same preference for certain genera, or certain families. To this may be added, that several foreign drugs, which were formerly supposed to be the production of a single plant, have been found on inquiry to be furnished by several species of the same genus ; and that with respect to indigenous simples it is no new thing, for species of the same genus to be substituted for each other. And we may observe, the narratives of travellers inform us, that plants of the same family are often employed for similar purposes in countries remote from each other,

Yet many exeeptions.

Resemblance

Notwithstanding these assertions however, which the author supports by several examples, it cannot be denied, that vegetables very closely allied present very striking anomalies. In order to estimate the real weight of these, the author takes a review of the rules of comparison between forms and properties, and this is the part of his work that displays most novelty.

1. In the first place he observes, that, though we arrange in some fami- species under genera, genera under families, and families unlies of plants

der

others.

der classes, in a uniform manner, the groups are far from be- closer than ing separated from each other in an equal degree Thus in certain families plants differ from each other by slight modifications only, while in others they are distinguished by more important characteristics. The analogy between their properties may be presumed to be proportional to the analogy of their structure.

2. Secondly, it is contrary to the spirit of the method, to Similar organs only and simicompare the properties of a given organ, or a given juice, lar juices with those of another organ, or another juice. This however should be comis one of the most frequent causes, that have led to mistakes pared.

on the question. In this discussion the author introduces by

the

way some new views respecting the structure of bulbs, the body of which he proves to be in reality an abortive stalk, and not a root.

circumstances

3. The circumstances of the age of a plant, the season in Adventitious which it is gathered, the soil in which it has grown, and the should be simidegree of light to which it has been exposed, are so many lar. causes of errour, that are to be avoided in the comparison.

sometimes un

4. Unequal mixtures or unequal combinations of different Principles principles are found in the organs or juices of certain fami- equally mixed lies; and in these families several of the most apparent ano- or combined. malies occur.

properties.

5. In the comparison of properties, we should pay atten- Modes of pretion to the difference that may exist in the mode of extracting paration alter and preparing a drug; for these circumstances frequently have as much influence on their properties as their intrinsic

nature.

6. We should exclude from the comparion the mechanical Accidental qualities must or accidental properties, that arise from circumstances inde- be excluded, pendent of the true nature of substances.

cular result but general mode

7. Above all we should most scrupuously attend not to the Not the arti result of the application of a medicine, but to its mode of acting; for medicines similar in reality act differently according of action to bɩ to the organ to which they are applied, or the case in which they are administered, and the contrary.

After laying down these principles the author takes a view of all the families, that compose the vegetable kingdom; and details the properties of all the plants that belong to them,

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regarded.

view of the

Mr. D's work including not only those that are admitted into our European a complete Pharmacopoeias, but those that are employed medicinally by properties of the inhabitants of any part of the globe. In this respect Mr. vegetables. Decandolle's work gives a complete and methodical display Of 76 families of the properties of vegetables: and the result of this exhibianalogy little tion is, that, of seventy-six families, the properties of which are known, there are thirty-seven where the law of analogy is violated, twenty-three where it is completely preserved, and forty-six in which it is observable with a small number of exceptions.

violated in 46, and not at all

in 23.

Lazulite of
Stiria.

Analysed by
Klaproth,

VI.

Analysis of the Siderite, or Lazulite; by Messrs. TROMMS-
DORFF and BERNHARDI*.

THE

HE lazulite was found at first near Waldbach, in Stiria, and afterward in the envirous of WienerischNeustadt. It is sufficiently known from the works of various mineralogists. Some time after a mineral was discovered in the country of Salzburg, which was called mollite; but baron Moll has given it the name of siderite, on account of its acknowledged identity with this fossil according to the researches of Mr. Mohs.

Though Klaproth found in the lazulite of Vorau silex, alumine, and iron, he could not ascertain their proportions, from the smallness of the quantity he had to examine. An and by Heim. analysis of the siderite by Heim gave 0.65 alumine, and

Little analo

spar.

0.30 iron.

It is strange, that Messrs. Klaproth, Estner, and Mohs, gous to feldt- should fancy there was a great analogy between the lazulite and feldtspar, as analysis shows this aualogy to be very slight; and that between their crystallizations and contexture is equally so.

Its usual form.

The most usual form of the lazulite is a regular octaedron with truncated edges, passing to the regular rhomboidal

Annales de Chimie, Vol. LXII, p. 43, April, 1807. Abridged from Gehlen's Journal by Mr. Vogel,

dodecaedron

dodecaedron. The faces of the octaedron make an angle of 109° 28′ 16′′: those of the dodecaedron an angle of 120°: and the former cut these at an angle of 144° 44′ 8′′. Beside these several smaller faces were observed, which were not easy to determine, because the specimens were not very distinct.

It is not uncommon to meet with flattened quadrilateral Varieties of prisms, the faces of which form angles of 101° 32′ and form. 78° 28'; angles that occur in several minerals, particularly in the calcareous spar. At the extremities of these prisms were faces in greater or less number, which we could not ascertain.

As to its contexture, we could not find it split decisively Not fissile. in any direction.

With respect to its crystallization it can be compared only Resembles the with the spinelle, with which Mr. Hauy classes the ceylanite spinelle.

or pleonast. As analysis informs us too, that it resembles it in its constituent parts, we must consider them as similar. The following is a comparative analysis of them.

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We find that alumine united with magnesia must be con

sidered as the essential part of the mineral.

As Mr. Bernhardi took upon himself to describe the chaacters of the lazulite, Mr. Trommsdorff attended more particularly to the analysis. He proceeded as follows.

Its analysis.

A. A hundred grains of siderite strongly calcined in a Calcined. covered crucible lost 5 grains of their weight. The fine blue colour had disappeared, and was changed to a yellowish

white.

B. The

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