Two principal schools of medical practice prevailed in the Old World during the greater part of the seventeenth century. The first held to the old methods of Galen: its theory was that the body, the microcosm, like the macrocosm, was made up of the four elements--fire, air, water, earth; having respectively the qualities hot, dry, moist, cold. The body was to be preserved in health by keeping each of these qualities in its natural proportion; heat, by the proper temperature; moisture, by the due amount of fluid; and so as to the rest. Diseases which arose from excess of heat were to be attacked by cooling remedies; those from excess of cold, by heating ones; and so of the other derangements of balance. This was truly the principle of contraries contrariis, which ill-informed persons have attempted to make out to be the general doctrine of medicine, whereas there is no general dogma other than this: disease is to be treated by anything that is proved to cure it. The means the Galenist employed were chiefly diet and vegetable remedies, with the use of the lancet and other depleting agents. He attributed the four fundamental qualities to different vegetables, in four different degrees; thus chicory was cold in the fourth degree, pepper was hot in the fourth, endive was cold and dry in the second, and bitter almonds were hot in the first and dry in the second degree. When we say “cool as a cucumber,” we are talking Galenism. The seeds of that vegetable ranked as one of “the four greater cold seeds” of this system. Galenism prevailed mostly in the south of Europe and France. The readers of Moliere will have no difficulty in recalling some of its favorite modes of treatment, and the abundant mirth he extracted from them. These Galenists were what we should call “herb-doctors” to-day. Their insignificant infusions lost credit after a time; their absurdly complicated mixtures excited contempt, and their nauseous prescriptions provoked loathing and disgust. A simpler and bolder practice found welcome in Germany, depending chiefly on mineral remedies, mercury, antimony, sulphur, arsenic, and the use, sometimes the secret use, of opium. Whatever we think of Paracelsus, the chief agent in the introduction of these remedies, and whatever limits we may assign to the use of these long-trusted mineral drugs, there can be no doubt that the chemical school, as it was called, did a great deal towards the expurgation of the old, overloaded, and repulsive pharmacopoeia. We shall find evidence in the practice of our New-England physicians of the first century, that they often employed chemical remedies, and that, by the early part of the following century, their chief trust was in the few simple, potent drugs of Paracelsus.