MEANS OF ASCERTAINING THE OPERATION OF MEDICINES.

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any particular species be injurious, neighbouring species are likewisemore or less so. Experience has fully proved that in a very large numberof instances there exists an analogy between the exterior forms and themedicinal properties of plants, so that we can sometimes predict theactive principle and mode of operation of a vegetable, merely by know-ing to what part of a natural arrangement it properly belongs. Cruciferee(fig. 1), for example, present the greatest uniformity in their botanical,chemical, and medicinal characters. They contain avolatile acrid principle, which renders them stimu-lant ; and having been employed successfully inscurvy, are frequently termed anti-scorbutics. TheLabiatm (fig. 2), which constitute, perhaps, the mostnatural family of the whole vegetable kingdom, con-tain a bitter resinous, or extractive matter, and anetherial, aromatic, or volatile oil; which two princi-ples, mixed in different proportions, are found inall the species, to which they communicate tonic and

Raplianus sativus.

Glechoma hederacea.

carminative properties. Neither Crucifer <e nor Labiates contain a singleFig. 2. unwholesome or even suspicious species. In Coni-fer® (fig. 3) we find the different species pervadedwith an oleo-resinous juice, in consequence of whichthey possess stimulant properties.—Many other fami-lies might be quoted to the same effect, and, therefore,we admit as a general rule, that plants of similar struc-ture possess similar medicinal qualities.

We are obliged, nevertheless, to admit the exist-ence of numerous exceptions. There are manyfamilies, the plants of which appear to possess thegreatest botanical affinity for each other, hut which are endowed withvery dissimilar remedial properties. Umbellifer ® (fig. 4)is an example of this. The root and leaves of DaucusCarota are wholesome and nutritive, hut the analogousparts of Coniurn maculatum are highly poisonous. Insome cases we even find plants of the same genus differ-ing considerably in their medicinal properties. I needonly mention in proof, Cucumis Melo and Cucumis Colo-cynthis. If we are to believe the statements of crediblewriters, even Gramme®, which Decandolle declares tobe “ la famille la plus naturelle,” contains more than oneexception to the general statement in question. Forthe most part the plants of this family are farinaceousand nutritive. “None,” says Dr. Lindley ( NaturalSystem), “ are unwholesome in their natural state, withthe single exception of Lolium temulentum (fig. 5), a com-mon weed in many parts of England, the effects of w hichare undoubtedly deleterious, although perhaps much ex-aggerated.” I may remark, however, that several othergrasses have been asserted to be unwholesome. Loudon{Ency clop a dia of Plants, p. 64) tells us that the seedsof Bromus mollis bring on giddiness in the human speciesPicea vulgaris and quadrupeds, and are fatal to poultry. The root of(Nees ab Esenbeck .)Bromus purgans is said to be used in Canada as an