Perhaps, however, botanical affinity may allow us to infer a similarity of action?
This is far from being the case, as there are many examples of opposite, or at least very different powers, in one and the same family of plants, and that in most of them. We shall take as a basis the most perfect natural system, that of Murray.
In the family of the coniferae, the inner bark of the fir-tree (pinus sylvestris) gives to the inhabitants of northern regions a kind of bread, whereas the bark of the yew-tree (taxus baccifera) gives-death.
How come the feverfew (anthemis pyrethrum), with its burning root, the poisonous cooling lettuce lactuca virosa), the emetic groundsel (senecio vulgaris), the mild scorzonera, the innocuous cudweed (gnaphalium arenarium), the heroic arnica (a. montana), all together in the one family of the compositae?
Has the purging globularia alypum anything in common with the powerless statice, both being in the family of the aggregatae? Is there any similarity to be expected betwixt the action of the skirret root (sium sisarum) and that of the poisonous water-dropwort (aenanthe crocata), or of the water-hemlock (cicuta virosa), because they are in the same family of the umbelliferae?
Has the not harmless ivy (hedera helix), in the family hederaceae, any other resemblance to the vine (vitus vinifera), except in the outward growth? How comes the harmless butcher's-broom (ruscus) in the same family of the sarmentaceae with the stupifying cocculus (menispermum cocculus), the heating aristolochia, and the asarum europaeum?
Do we expect any similarity of effect from the goose-grass (galium aparine) and the often deadly spigelia marylandica, because they both belong to the stallatae? What resemblance can we find betwixt the action of the melon (cucumis melo) and the elaterium (momordica elaterium), in the same family of the cucurbitaceae?
And again, in the family solanaceae, how comes the tasteless great mullein (verbascum thapsus), along with the burning Cayenne pepper (capsicum annuum); or tobacco, which has such a powerful spasm-exciting action on the primae viae, with nux vomica, which impedes the natural motions of the intestines?
Who would compare the unmedicinal perriwinkle (vinca pervinca) with the stupifying oleander (nerium oleander), in the family contortae? Does the watery moneywort (lysimachia nummularia) act similarly to the marsh trefoil (menyanthes trifoliata), or the powerless cow-slip (primula veris), to the drastic sowbread (cyclamen europaeum), in the family of the rutaceae?
From the strengthening effects of the bear-berry (arbutus uva ursi) on the urinary apparatus, can we infer the heating, stupifying action of the rhododendron chrysanthum, in the family bicornes?
Among the verticillatae, can any comparison be made betwixt the scarcely astringent self-heal (prunella vulgaris) or the innocent bugle (ajuga pyramidalis), and the volatile germander (teucrium marum), or the fiery majoram (origanum creticum)?