T h e want of an exaCt knowledge from what plant this
or that particular medicine is taken, is not one of the
leaft caufes of the prefent imperfection of the Hiftory of
Phylic | and notwithftanding the extenfivenefs of commerce
in thefe latter times, and the opportunities thereby
afforded to the cultivators of Natural Hiftory o f examining
the productions of various countries in their
native foil, and-even in regions from whence felf-intereft
had before e x c lu d e d them, we are ltill ignorant from
whence feveral medicines are prepared, which we every
day rffe in the practice of Phyfic. To this ignorance
muft likewife be attributed that uncertainty which prevails
in the operations of particular medicines, and the
different opinions which have prevailed relative to their
effeCts on the human body ; and this relates not only to
fuch vegetables as are brought from diftant regions,
but even to thofe which are natives of our own country.
From the hotter climates we receive feveral medicines,
which, though coming from different places, are
called by the fame title; and many European plants are
in one place commended for their lingular efficacy,
A while