62 Professor Burnett’s 
the equally important facts, that certain specimens of bark 
submitted to his examination contain a large, and others a 
small, portion of one or other of the active or inert principles, 
without the botanist could indicate the plants which yield 
them, and teach to distinguish those in which the active 
agents the most abound, and which consequently may be the 
most profitably employed? Say not that the merchant or 
the druggist will import and prepare them to his hand: this 
would indeed be trusting to a rotten staff, without they were 
themselves instructed in that science which alone can teach 
to distinguish those which are found less from those which are 
found more efficient in their use and productive of the active 
agents sought. Are crops to be cultivated and cargoes to be 
imported on chance or bare empirical presumption, and the 
first notice of error be in the disappointment of the physician 
at the non-efficacy of his prescription, or in the vain labour of 
the chemist to extract the essential parts? 
Besides the certain diagnoses it affords, there is another 
advantage of botanical system, especially of the natural sys- 
tem, which, although it is very much perverted and abused, 
holds, in my mind, a rank of no mean importance: viz. the 
general rule, sanctioned by experience, that plants possess- 
ing the same botanical characters often contain the same 
chemical principles, and produce the same medicinal effects; 
not always, indeed seldom, in a similar degree, but most fre- 
quently in a graduated scale. The potency being traceable 
in the various instances from its least to its greatest accumu- 
lation, from its lowest to its highest stages of activity. ‘Thus, 
the Lactuca virosa is highly acrid, while the Lactuca sativa is 
bland and esculent; the Cucumis sativus an agreeable food, 
while the Cucumis colocynthis is a powerful medicine; the 
Vegetable Marrow, Gourds, and Melons, mild and innoxious, 
while the Momordica Elaterium is so violent in its effects as 
almost to be esteemed a poison. Again, the Croton Casca- 
rilla is a grateful stomachic, while the Croton Tiglium is a 
most violent cathartic; the Leopard’s bane may be contrasted 
with the artichoke, and parsley with hemlock; the Solanum 
dulcamara, nigrum, and tuberosum, bear hurtful berries; 
while those of the egg-plant and the tomato, when cooked, 
form a wholesome food; the pea and bean are only flatulent, 
while the laburnum is a poison. And furthermore, so com- 
pletely are the latent properties of some plants developed in 
other individuals of the same species, genera, and orders, 
while the notorious principles of those are overshadowed or 
become occult in these, that, did not instances occur in dif- 
ferent varieties of the same species, and different species of 
