After the Arabians, from the twelfth to the fifteenth century, the practice of medicine was chiefly confined to the hands of the priests, who, being men of great learning and followers of Aesculapius, Hippocrates, and Galen, became the principal physicians, and a little medicine was taught in the monasteries; for a long time the Benedictine monks of Monte Casino enjoyed in this respect great reputation. The Jews also became celebrated physicians; and though not allowed to administer medicines to Christians, yet obtained access to the courts, and even to the palace of the Roman pontiffs.

The European feudal system was at length greatly shaken by the Crusades. MAHOMET the second, about the middle of the fifteenth century, captured Constantinople, and soon after the ruin of the Byzantine empire, the Reformation occurred, and about the same time the art of printing was invented. These events gave a powerful impulse to the world of mind, and reawakened investigation into all the departments of science, literature, and the arts; but, although many works were written, very few facts were gleaned concerning the physiological, anatomical, and pathological phenomena incident to the Structure, Health, and Disease of the human being.

The alchemic art, however, was at length transferred from Arabia into European countries, and medical chairs were established in various Universities on the continent during the thirteenth century, and finally LINACRE, who had been educated at Oxford, and having traveled in Italy, and spent some time at the court of Florence, returned to England, and succeeded in founding medical professorships at Oxford and Cambridge, from which circumstance was laid the foundation of the London College of Physicians. Thus chemistry, after having been employed in various pharmaceutical processes, was applied to physiology, pathology, and therapeutics. The chemical doctors were very wild and extravagant in advancing unnatural theories; but they had an ever-present champion in the name of Galen, who was well entitled to be called the "Prince of Medical Philosophers."  He was a philosopher -- a natural philosopher; for he studied Nature closely, deeply, profoundly, and deduced his indications of cure from an accurate observation of her laws. His system, however, was destined to be utterly overthrown by an adventurous vagrant, whose quackery never had its equal on earth. This impudent and unprincipled charlatan was none other than Paracelsus, to whom the medical world is more indebted for the mineral drugging system than to all other physicians who have ever lived. He introduced the mercurial and antimonial practice, which still constitutes the great strength of the popular materia medica of the day, and which also continues to exhibit its terribly devastating power on all human constitutions that come under its sway or influence. In the fulness of his pride, pomp, and arrogance, Paracelsus burned, with great solemnity, the works of Galen and Avicenna, declaring that he had found the philosopher's stone, and that mankind had no further use for the medical works of others. He lived a disappointed vagabond, and died prematurely at the age of forty-eight, his famous elixir vitae having failed to save him from a most horrible fate. Still his abominable doctrines prevailed, and his infatuated followers have added several hundred other chemical or mineral preparations to the materia medica of the great Quicksilver Quack. At the prsent day, among a certain class of physicians, there is hardly a disease in the catalogue of human ailments in which the employment of mercury, antimony, arsenic, and other deadly drugs is not employed.

During the seventeenth century the doctrines of Hippocrates again rose to some consideration in medical philosophy. Anatomy made progress. HARVEY discovered the circulation of the blood; others traced out the absorbent system, and explained the functions and structure of the lungs; while BOYLE disengaged chemistry from the mystery by which it was surrounded, and explained its true province to be, "not the manufacture of solid gold, nor liquid nostrums, nor gaseous theories, but an investigation into the change of properties which bodies experience in their action upon each other.

From this time to the beginning of the eighteenth century, notwithstanding many facts had accumulated in chemistry, anatomy, and physiology, physicians, as a body, held no more natural views of the true nature of disease than were advanced by Hippocrates three thousand years before. Indeed, it is positively certain that none of the most eminent new schools or sects of the present day had been more successful in curing diseases than were Hippocrates, Galen, and Sydenham. Meantime, however, there have arisen physicians who, while they readily received all new facts in respect to the structure of the human organism, still adhered to the instinctive inductions of Nature, and treated diseases with most abundant success by means of Herbal preparations alone. We have at this day as bright a galaxy of names -- scholars, philosophers, philanthropists, and humanitarians -- as ever adorned any age of the world, devoting themselves with a zeal and industry worthy of all praise to the study and practice of medicine, but, failing to perceive the grand results anticipated in their laborious researches after truth, do not hesitate to admit that our actual information does not increase in any degree in proportion to our experience. All their array of learning, and their multitudinous writings, have only served to make confusion worse confounded, and all from the very simple fact that they have neglected to follow the requirements of Nature and common sense, in maintaining the Herbal Practice as the only true and philosophical foundation of the Healing Art. Admidst all the jarrings, conflicts, and dogmas of the medical world, is it any wonder that the great masses are rapidly losing all confidence in Medical Science, and crying for a more natural system of medication -- even one founded in the principles of irrefragable Nature? With this view I have devoted many years of my life, and having traveled in numerous lands, I feel that I am now qualified, from a long medical experience and deep research into the physiology of Plants, to present to the world of suffering humanity all those curative elements best calculated to ensure perfect health, and the utmost length of life, to all who may feel disposed to be guided by the doctrines and system of medication which it is the object of this volume to make known.