The Arabian author, Ibn Al-Beithar (b. ca. 1197 A.D.), describes a stone called in Arabic _hajer al-kelb_, or “dog-stone.” These stones had such attraction for dogs of a certain breed that when cast before them they would snap them up, bite them, and hold them in their jaws. The magicians saw in this a proof that the stones would produce enmity and ill-will among men. Having selected seven such stones they marked them with the names of any persons between whom they wished to stir up strife. The seven stones were then thrown one by one before a dog of the requisite species, and, after he had bitten them, two were chosen and were placed in water of which the persons who were to be set at variance were sure to drink. We are assured that the experiment had the desired evil result.[20] In ancient times there was found in the river Meander a stone satirically named _sophron_, “temperate.” If it were placed upon the breast of any one, he immediately became enraged and killed one of his parents; however, after having appeased the Mother of the Gods, he was cured of his temporary madness.[21] A most singular stone is described by Thomas de Cantimpré under the name of “piropholos.” This substance, according to Konrad von Megenberg’s version, was taken from the heart of a man who had been poisoned, “because the heart of such a man cannot be burned in fire.” If the heart were kept for nine years in fire this wonderful stone was produced. It gave protection from lightning, but its principal virtue was to guard the wearer from sudden death; indeed, we are told that a man could not die so long as he held this stone in his hand. However, it did not preserve him from disease, but only prolonged his life. The stone was said to be of a light and bright red color.[22] After enumerating all the well-known precious stones, Volmar, in his “Steinbuch,” proceeds to relate that there is one which produces blindness, another that enables the wearer to understand the language of birds, still another that saves people from drowning, and, finally, one of such sovereign power that it brings back the dead to life. However, we are told that because of the miraculous virtues of these stones God hides them so well that no man can obtain them.[23] About a century earlier Saint Hildegard of Bingen wrote that “just as a poisonous herb placed on a man’s skin will produce ulceration,” by an analogous though contrary effect “certain precious stones will, if placed on the skin, confer health and sanity by their virtue.”[24]