points out the countries and climates which different families affect ; and gives us principles for their cultivation, either as medicines, or as objects of agriculture : the other is no less valuable in affording us innumerable indications in every part of the world, for discovering the properties of new and unknown plants, whether as fitting them for food, for medicine, or for any of the arts of life ; and though there are no doubt exceptions, (fewer, however, than usually adduced) there certainly is no other method by which we may so readily find a substitute for a medicine, or an equivalent for an article of trade, as by seeking for it in the families of plants, which are already known to contain some possessed of such properties as we desiderate. This is no trivial advantage ; for though our Pharma- copoeias and Dispensatories may be models of what is requisite for civilized society, yet if it be considered that the English Schools of Medicine supply practitioners for an empire, on which, without hyperbole, it has been said, the sun never sets ; it will readily be allowed, that we may frequently be placed where there are neither chemists to analyse, nor herbalists to select the plants, secreting most valuable products at our feet; but to which we might readily be led by studying their natural affinities. Our systems of Materia Medica might therefore inculcate these more comprehensive doctrines, and a teacher extend the range of his influence and usefulness, while describing any officinal species, by introducing it with general observations on the family to which it belongs, as well as the countries where this is chiefly found. An Indian sage, after giving a prescription of precious stones, for curing the diseases of kings and rich men, very judiciously adds another, for people in general, composed of vegetables, because these are procurable by all.
The system of arrangement, however, alone applicable
