PREFACE.

HAVING AVING long meditated the commencement of a work on the medicinal vegetables of the United States, and feeling myself obligated for its completion, by the instructions from the Univer sity in which I have the honor to hold a professorship; it may be proper to make at the outset some general statements of the motives and objects of such a publication.

The Materia Medica, comprising the great body of medicinal agents now in use in the hands of physicians, cannot be said to need an increase in the number of its articles. It is already incumbered with many superfluous drugs; even its active substances are more numerous than can be of use to any one physician, so that it seems quite as susceptible of benefit from reduction as from augmentation in the number of its materials, Under these circumstances, the introduction of new medicines can only be authorized, where

from the peculiarity of their powers, or the facility of their acquisition, they are calculated to take the place of others previously in use.

Of our present stock of medicinal agents, collected from various parts of the globe, a few appear to be unique in their powers, and could not in the present state of our knowledge, be superseded by other substances. A number more possess active properties, yet of a kind, for which substitutes might be found among the native productions of almost every country into which they are imported. There are others which possess little activity or value, but which, from a sort of fashion, are still articles of commerce and consumption.

In the management of diseases, the physician requires instruments of determinate power, on the operation of which, he may build definite expectations. Many such are already in his hands. Yet when we consider how small a portion of the vegetable kingdom has been medically examined, there can be little doubt that a vast number of active substances, many perhaps of specific efficacy, remain for future inquirers to discover. In this respect, every successive age is making acquisitions. But a century or two ago, the civilized world were unacquainted with the properties of ipecacuanha, of jalap, and the Peruvian

bark. The powers of digitalis in certain diseases are of very recent observation. At the present day, we are speculating on the probable composition of a vegetable medicine, which cures the gout.

Medicinal substances frequently owe their first introduction to accident. Many have been at first brought up as antidotes for the poison of serpents, as remedies for syphilis, or as specifics against imaginary diseases. Previously to this, they were neglected as useless, or avoided as dangerous. It is a subject of some curiosity to consider, if the knowledge of the present Materia Medica were by any means to be lost, how many of the same articles would again rise into notice and use. Doubtless a variety of new substances would develop unexpected powers, while perhaps the poppy would be shunned as a deleterious plant, and the cinchona might grow unmolested upon the mountains of Quito.

It is the policy of every country to convert as far as possible its own productions to use, as a mean of multiplying its resources, and diminishing its tribute to foreigners. The plants of the United States are various in their character in proprotion to the extent of latitudes and climates, which our country embraces. Among those which