put a mouse in a dish of water and then give this water to the patient to drink, not to mention washing his forehead and feet in it. As with drinking Postum instead of coffee, "There is a reason." It is this,
Marbod and Hildegard were twelfth-century writers, and somewhat naïve and undiscriminating in their acceptance of marvels. The thirteenth-century encyclopedias and works on medicine do not contain so much chaff in proportion to their wheat; but they still contain a great deal. Even Roger Bacon, who declared false and disproved by experiment several such notions as that only goat's blood can break adamant and that hot water freezes faster than cold,—even Bacon still speaks of the "almost miraculous" powers of "herbs and stones and metals." However, the writers come to recognize that there is something peculiar and requiring explanation in these strange properties ascribed to the things of nature. In the thirteenth century they are distinguished as occult virtues and are regarded as marvelous. It is admitted that reason can not account for them, but their existence is declared to be attested by experience.
Thus Albertus Magnus admits that it is difficult to explain the strange virtues of gems, and says that many students of nature seem to doubt whether stones possess any such attributes as to cure ulcers, counteract magic potions, conciliate human hearts, and win battles. But he insists that these occult virtues are well-established facts, and gives two examples attested by his own experience, namely, the magnet's power to attract iron and a sapphire which he saw cure ulcers. Some plants, too, Albert declares, have "divine effects which students of magic especially investigate."
On the other hand, Vincent of Beauvais, while he still agrees with Marbod that the virtues of gems are so marvellous that they can be accounted for only as the result of direct divine influence, thinks that plants possess only natural powers, which are chiefly medicinal. Nor does either Albert or Vincent usually recommend fantastic or irrelevant methods of using herbs medicinally. Many, however, of the medicinal virtues which they ascribe to plants are probably false, and they also show a tendency to make each plant a panacea for a long list of very miscellaneous and unrelated diseases. This may be illustrated by a passage taken quite at random and which happens to be about the nasturtium: