The facts hitherto collected upon this subject are so scanty and
unsatisfactory, that I introduce its consideration in this place, rather
with a wish to excite farther enquiry, than with any hope of imparting
much additional information.
There can be little doubt, but that Soil, Culture, Climate, and
Season,[118] may very materially influence the active properties of a
medicinal plant; while the two latter of these causes may as essentially
change the type and character of a disease, and modify the vital
susceptibility of the patient; the natives of the south of Europe, for
instance, do not bear bleeding, and other modes of depletion, so well as
those of the north. This must be admitted to its full extent, or it will
be extremely difficult to explain the contradictory and even opposite
opinions, and to reconcile the conflicting testimonies of the physicians
of different countries, with respect to the efficacy of the same remedy,
in similar diseases.
THE INFLUENCE OF SOIL may be exemplified by many well known facts; thus,
strongly smelling plants lose their odour in a sandy soil, and do not
again recover it by transplantation into a richer one; a fact upon which
Rozier founded his proposal for the improvement of Rape oil; so again,
no management could induce the _Ricotia Ægyptiaca_ to flower, until
Linnæus suggested the expediency of mixing clay with the earth in the
pot; _Assafœtida_ is one of those plants that vary much according to
station and soil, not only in the shape of the leaves, but in the
peculiar nauseous quality of the juice which impregnates them, and Dr.
Woodville states that it is frequently so modified that the leaves are
eaten by goats; Gmelin informs us, on the authority of Steller, that the
effects of the _Rhododendron_ have been found to vary materially
according to the “_solum natale_;” for example, that produced in a
certain spot has proved uniformly _narcotic_, that in another,
_cathartic_, while a sense of suffocation has been the only symptom
occasioned by a third. Rhubarb, as grown in England, will differ greatly
in its purgative qualities, according to the soil in which it may have
been cultivated; that produced in a dry gravel being more efficacious
than that which is reared in a clayey one. Dr. Carter, in his account of
the “_Principal Hospitals of France, Italy, and Switzerland_,” tells us
that at Nice, the _Digitalis_ is commonly given in doses of a scruple in
powder, or in that of half an ounce of the infusion made according to
the London Pharmacopœia, every hour, and without any sensible effect;
this fact he explains by stating that the _Digitalis_, in the
neighbourhood of Nice, is much smaller, and is probably less powerful
than the same plant as it grows in England.
CLIMATE also produces a powerful impression upon vegetable and animal
life. It is probable that in southern countries some vegetables enjoy
more energetic properties than in northern climes. The history of opium
immediately countenances such an opinion; thus Egypt produces a stronger
_opium_ than any of the countries on the north side of the
Mediterranean,—France, than England or Germany;—and Languedoc, than the
northern parts of France;—while Smyrna, Natolia, Aleppo, and Apulia,
furnish a juice far more narcotic than Languedoc: so again, _Senna_ by
transplantation from Arabia into the south of France (Provence) assumes
a marked change in its physiognomy and virtues, its leaves are more
obtuse, and its taste less bitter and nauseous than the pointed leaved
variety, while its effects will be found to be less purgative.
_Cruciform_ plants degenerate within the tropics, but acquire increased
energies, as _Antiscorbutics_, in cold regions; the _Menthæ_ have not so
penetrating an essential oil in the south of Europe as in England and in
the north of France. The relative proportions of gluten vary in the
wheat of different countries, and as in the south of Europe, its
quantity greatly predominates over the other principles, we at once
discover the cause that gives such excellence to the Maccaroni of Italy.
Many species of plants secrete juices in warmer regions, which are
unknown in their œconomy, in colder climates; thus the Ash yields
_Manna_ in Calabria, but loses that faculty as it advances towards the
north. The influence of climate, in its relations to moisture and
dryness, upon vegetable productions, is also worthy of investigation; in
wet and cold seasons, our herbage is far less nutritive to cattle, and
we accordingly find that they are constantly grazing, in order to
compensate by quantity, for what is deficient in quality, whereas in dry
seasons, a larger proportion of their time is consumed in rumination;
the same causes, however, that diminish the nutritive powers of plants,
frequently increase the energy of those principles upon which their
medicinal value depends: it is obvious that many herbs are more rank and
virulent in wet and gloomy seasons: this would appear to be a wise and
provident law, in order to apportion the natural condiment of the
vegetable, to the deteriorated state of its nutritive elements, when the
digestive organs must require more than the ordinary stimulus for the
due exercise of their functions. It is hardly necessary to observe that
plants, which in temperate climates are merely shrubs, have been
developed into trees, by the hot and humid plains of Africa and Asia;
while in the arid deserts of Nubia or in the frigid plains of Siberia,
vegetable life is confined to stunted shrubs and humble mosses: cold
also suppresses the colour of flowers, and indeed even that of the
leaves, as is witnessed in the _Cyclamen_, _Amaranthus_, and
_Ranunculus_ of Lapland and Siberia. But climate not only modifies the
powers of a remedy by influencing its structure and composition, but it
renders it more or less active, by increasing or diminishing the
susceptibility of the body to its impression; can a more striking proof
of this fact be adduced than the well known effects of perfumes at Rome?
The inhabitants are unable to sustain the strong scent of flowers in
that climate, without experiencing a sensation highly oppressive, and
which in some cases is even succeeded by syncope,[119] and thus
realising the well known line of the poet,
“_Die of a Rose, in aromatic pain._”
As I have been favoured with some very interesting observations upon
this subject by Dr. Richard Harrison, who resided for a considerable
time in Italy, and was thus enabled to institute a satisfactory inquiry
into this curious subject, I feel no hesitation in introducing a
quotation from his letter to my readers.—“You ask me what experience I
have had on the subject of climate, as affecting the powers and
operation of remedies; I have no difficulty in asserting that Narcotics
act with greater force even in smaller doses at Naples, where I had the
advantages of much experience, than in England. I might adduce as an
example the _Extract of Hyoscyamus_, which, when given to the extent of
three grains thrice a day, produced in two patients a temporary
amaurosis, which disappeared and again recurred on the alternate
suspension and administration of this medicine; and it deserves
particular notice that these very patients had been in the habit of
taking similar doses of the same remedy in England, without any
unpleasant result. Now that this depended upon an increased
susceptibility of the patient, in the warmer climate, rather than an
increased power in the remedy, is unquestionable, since the extract
which was administered in Italy had been procured from London; indeed a
high state of nervous irritation is the prevalent disorder of Naples. I
treated several cases of Epilepsy in Italy with the _nitrate of silver_,
and with complete success, while in England I certainly have not met
with the same successful results. During my residence at Naples, I spent
some time in the island of Ischia, so celebrated all over the continent
for its baths; many of the patients who were then trying their efficacy,
had been attacked by Paralysis, Apoplexy, and almost every degree of
loss of mental and muscular power, and among them I certainly witnessed
what with propriety might be denominated a genuine case of _Nervous
Apoplexy_. These complaints I was generally able to trace to the abuse
of _Mercury_, whence we may, I think, very fairly conclude that this
metal is more active in its effects in that, than in our own country.
Before I quit this subject, I ought to mention that the doses of
medicines, as seen in the prescriptions and works of English Physicians,
excite universal astonishment among the faculty of Italy. In fact, as I
have just stated, the human constitution in this part of the continent
is certainly more susceptible of nervous impression than in England: it
is perfectly true that flowers or perfumes in a chamber, will frequently
produce syncope in persons apparently strong and healthy, and the fact
is so universally admitted, that the Italians avoid them with the
greatest caution.” On the other hand, it appears equally evident that
some remedies succeed in cold climates which produce little or no
benefit in warmer latitudes. Soon after the publication of the first
edition of my Pharmacologia, I received a letter from Dr. Halliday of
Moscow, upon the subject of the “_Eau Medicinale_,” and as it offers a
striking proof of the efficacy of the _Rhododendron Chrysanthum_ in
curing the rheumatism of the North, whilst in this country the plant has
been repeatedly tried without any signal proof of success, I shall here
subjoin an extract from the letter of my correspondent: “In reading your
account of the ‘_Eau Medicinale_,’ I perceive that, upon the authority
of Mr. James Moore, you state it to be a preparation of the _White
Hellebore_; may I be allowed to suggest the probability of its being
made from the leaves of the _Rhododendron Chrysanthum_? for so far as I
can learn, the effects of the French medicine are precisely those which
are experienced from an infusion of the above plant, which the Siberians
and Russians regard as an infallible specific in the cure of chronic
rheumatism and gout, and from which I myself, as well as other
physicians in Russia, have witnessed the most desirable and decided
effects, whenever we had it in our power to administer the remedy with
confidence and courage. We have seldom given it in any other form or
dose than that adopted by the Siberians themselves, which is to infuse
in a warm place, generally near a furnace and during the night, two
drachms of the fresh leaves in about twelve ounces of boiling water,
taking care that the liquid never boils. This dose is to be taken in the
morning upon an empty stomach, and during its nauseating operation,
which generally commences within a quarter of an hour after it has been
swallowed, neither solids nor liquids of any description are allowed;
after an interval of three or four hours, I have seen the patient obtain
a copious and black fœtid stool, and get up free from pain. Should it
happen that the patient does not recover from the first dose, another is
administered on the succeeding day, and I have known it to be taken for
three days in succession, when the severest fits of gout have been
removed.[120] Is it not then probable that some cunning Frenchman has
availed himself of this Siberian specific, and concentrated it in such a
form, as to defy all the learned to find it out?”
Dr. Halliday adds, “The Siberians denominate the leaves of this plant,
when infused in water, _Intoxicating Tea_; and a weaker infusion is in
daily use, especially for treating their neighbours, just as the
Europeans do with tea from China.”
Before we quit the consideration of Climate, as being capable of
influencing the activity of a remedy, the important fact should not be
overlooked, that in India, and other colonies of similar temperature,
Mercurial Medicines, in order to produce their beneficial effects,
require to be administered to an extent which would prove destructive to
the inhabitants of this island.
But of all the circumstances that produce the greatest change in the
aspect as well as in the virtues of the vegetable creation, is
CULTIVATION, which may either destroy the medicinal properties of a
plant, or raise in it new and most valuable qualities: cultivation
converts single into double flowers, by developing the stamens into
petals, a change which in many cases destroys their efficacy, as in the
camomile, _Anthemis Nobilis_; for, since all the virtues of this flower
reside in the disc florets, it is of course greatly deteriorated by
being converted into the double-flowered variety; by the operation of
_grafting_ extraordinary changes may also be produced; Olivier, in his
travels, informs us that a soft _Mastiche_, having all the qualities of
that resin, except its consistence, which is that of turpentine, is
procured by engrafting the Lentisk on the Chian Turpentine tree.
Buffon states that our wheat is a factitious production raised to its
present condition by the art of agriculture. M. Virey[121] observes,
that by suppressing the growth of one part of a plant we may
respectively give rise to an increased developement in others; thus are
some vegetables rendered eunuchs, or are deprived of seeds by
obliteration, and only propagate themselves by slips; such a condition
is frequently produced by culture, continued through a long succession
of generations; this is the case with the _Banana_, _Sugar Cane_, and
other fruits that have carefully been made to deviate for a long series
of years from their original types, and having been continually
transplanted by slips, suckers, or roots, at length only propagate
themselves in this way, whereby the roots, as those of the common
potatoe, become inordinately developed, drawing to themselves the
succulence and nutrition originally possessed by the berries. It seems
probable that we may thus have lost many vegetable species; the
_Tuberes_ of Pliny, for example, are supposed by Mr. Andrew Knight to
have been intermediate productions, formed during the advancement of the
Almond to the Peach, or in other words that they were swollen almonds or
imperfect peaches; if this conjecture be admitted, it will explain the
fact stated by Columella, that the peach possessed deleterious qualities
when it was first introduced from Persia into the Roman Empire. If there
be any who feel sceptical upon the subject of such metamorphoses, let
him visit the fairy bowers of Horticulture, and he will there perceive
that her magic wand has not only converted the tough, coriaceous
covering of the Almond into the soft and melting flesh of the Peach, but
that by her spells, the sour Sloe has ripened into the delicious Plum,
and the austere Crab of our woods into the Golden Pippin; that this
again has been made to sport in endless variety, emulating in beauty of
form and colour, in exuberance of fertility and in richness of flavour,
the rarer productions of warmer regions, and more propitious climates!
In our culinary vegetables the same progressive amelioration and
advancement may be traced; thus has the acrid and disagreeable _Apium
graveolens_ been changed into delicious _Celery_, and the common
_Colewort_, by culture continued through many ages, appears under the
improved and more useful forms of Cabbage, Savoy, and Cauliflower. It
has been already observed that the alimentary and medicinal virtues are
frequently in opposition to each other, and that while cultivation
improves the former, it equally diminishes the latter; I shall have
occasion to offer some additional facts upon this curious subject, under
the consideration of _Bitter Extractive_; _see Note on this Extract, in
the article_ “_Tonics_.”