The terrible plague known as the Black Death is said to have claimed 13,000,000 victims in Europe in the years 1347 and 1348. A contemporary, Olivier de la Haye, in a poem describing this fearful visitation, gives a number of recipes used, or to be used as remedies. In one of these there appear as ingredients pearls, jargoons, emeralds and coral, one-sixth of a drachm of each of these materials entering into the composition of the prescription.[228] The symptoms of this form of the plague, as described by the old writers, are said to resemble closely those of the disease that was prevalent not long ago in some parts of Asia, especially in northern China and Manchuria. A famous class of medical remedies used in medieval times bore the generic name _theriaca_, or theriac, this designation being derived from the Greek _therion_, signifying a beast, more specifically a poisonous animal and hence also a serpent. These preparations were primarily antidotes for poison, but were also freely administered for any form of “blood-poisoning,” for malarial infection, malignant fevers and the like. Principal ingredients were the “Armenian stone” (a friable, blue carbonate of copper), pearls, charred stag’s-horn, and coral. The Veronese physician, Francesco India, confidently affirms that this remedy not only cured the plague, but also protected those who had partaken of it from contracting the disease; this was said to be more especially true of the _theriaca Andromachi_, or Venice treacle as it was popularly called, which purported to be the invention of a Roman or Greek physician, Andromachus, who composed some medical poems dedicated to Cæsar.[229] In medieval Bohemia the knowledge of precious stones and their employment for curative purposes is well attested. There exists a Bohemian manuscript list of precious stones dated in 1391, in which no less than 55 different gems are noted. Their medicinal use in Bohemia at this time is vouched for by the Synonima Apothecariorum where precious stones are listed among the materials of the apothecaries’ art.[230] In the testaments of royal and princely personages, medical stones are often bestowed as precious legacies. Thus in the will of the Hessian prince, Henry VIII of Fürstenberg, the following stones are mentioned as especially costly objects: a “crabstone” (Krebstein), a bloodstone, and a gravel-stone, the latter being a piece of jade or nephrite.[231] The crabstone, sometimes called crab’s-eye, is a chalky concretion which forms on either side of the stomach of a crab or other crustacean during the moulting period, and this was and is still used as an eye-stone for the removing of foreign bodies that have entered the eye, the eye-stone being introduced under the eyelid. This results in a rapid flow from the tear-ducts which often washes away the foreign bodies, the passage of the stone across the eyeball occasionally aiding in the work by rubbing off the body. [Illustration: