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SPECIAL PHARMACOLOGY.

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Special Pharmacology (Pharmacologia specialis) treats of medicinesindividually.

Natural-Historical Classification of Medicines. —Having previouslystated that the natural-historical order will he followed in describing thedifferent substances composing the Materia Medica, it will not, 1 conceive,be out of place to offer a few general remarks on the division of naturalbodies into kingdoms, and on the characteristics of these kingdoms.

Natural bodies were formerly divided into three groups, called king-doms—the mineral, the vegetable, and the animal; but this division has,of late years, been for the most part given up, on account of the impossi-bility of so characterizing the two latter as to distinguish them fromeach other. To obviate this difficulty the two have been formed intoone, under the name of the organized or living kingdom, while the mineralis now called, in contradistinction, the inorganized kingdom.

But it has been asserted that no real distinction exists between theorganized and the inorganized kingdoms. There is an order of animalscalled, on account of their supposed resemblance to a mass of mineralmatter, the Lithozoa, or stone-animals (Goldfuss , Grundriss der Zoologie .)In these the skeletons are external, or cutaneous, and consist of carbonateof lime (sometimes with a little phosphate) agglutinated by gelatinousmatter. These beings have been supposed to connect the animal witlithe mineral kingdom. But the calcareous masses of the Lithozoa aremostly porous, and in the recent state contain fleshy tubes, constitutingthe soft parts of the animal: a structure nothing analogous to which isfound in the mineral kingdom. In the Nullipora (a family of the orderLithozoa) the pores are not evident, and hence these masses have beensupposed to form the nearest relation to minerals.

Vegetables also have been stated to be closely related to animals. Here

Fig. 31. is a drawing of the Diatoma vulgaris (Fig. 31), a littlevegetable of the family Algoe: it varies in its form, andin the mode of connexion of its parts. At one period ofits existence it is cylindrical, at another it is composedof quadrangular segments; sometimes connected by theirsides, at others by their alternate, angles. It will be ob-served that these segments have somewhat the forms andappearance of crystals ; and Agardli has, in consequence,fancied they form a distinct passage from vegetablesto minerals ; but their active properties, and the changesthey undergo at the different periods of their existence,sufficiently distinguish them.

Some zoologists (as Goldfuss ) admit an order of ani-mals which they call Phytozoa, or the vegetable-animals,(as Spongia) and which includes all those animals whichresemble plants. In some cases animals resemble flowersH

Diatoma vulgaris.