The belief in the existence of a stone of magical properties in the head of the toad is only one of the many instances of beliefs of a closely similar kind which were accepted by Pliny (although he records no such belief as to the toad-stone), and were passed on from his treatise on natural history in a more or less muddled form to the middle ages, and so to our own time by later writers. Thus Pliny cites, as stones possessing magical properties, the "Bronte" found in the head of the tortoise, the Cinaedia in the head of a fish of that name, the Chelonites, a grass-green stone found in a swallow's belly, the Draconites, which must be cut out of the head of a live serpent, the Hyaenia from the eye of the Hyaena, and the Saurites from the bowels of a green lizard. All these and the Echites, or viper-stone, were credited with extraordinary magical virtues, and many of the assertions of later writers about the toad-stone are clearly due to their having calmly transferred the marvellous stories about other imaginary stones to the imaginary toad-stone. The only stone in the above list which has a real existence is that in the fish's head. Fish have a pair of beautiful translucent stones in their heads--the ear-stones or otoliths--by the laminated structure of which we can now determine the age of a fish just as a tree's age is told by the annual rings of growth in the wood of its stem. The fresh-water crayfish has a very curious pair of opaque stones (concretions of carbonate and phosphate of lime) formed in its gizzard as a normal and regular thing. They are familiar to every student who dissects a crayfish, and I am told that in Germany to-day, as in old times also, the "krebstein" is regarded by the country-folk as possessed of medicinal and magical properties. I am not able, on the present occasion, to trace out the possible origin of all the stories and beliefs about stones occurring within animals. They are more numerous than those cited by Pliny; they exist in every race and every civilization and refer to a large variety of animals. Probably many of these beliefs date from prehistoric times. In the East the most celebrated of these stones, since the period of Arabic civilisation, is called a bezoar-stone, "Bezoar" is the Persian word for "antidote," and does not apply only to a stone. The true and original "bezoar-stone" of the East is a concretion found in the intestine of the Persian wild goat. Those which I have seen are usually of the size and shape of a pigeon's egg and of a fine mahogany colour, with a smooth, polished surface. The Persian goat's bezoar-stone is found, on chemical analysis, to consist of "ellagic acid," an acid allied to gallic acid, the vegetable astringent product which occurs in oak-galls used until lately in the manufacture of ink. The bezoar-stone is probably a concretion formed in the intestine from some of the undigested portions of the goat's food. Such concretions are not uncommon, and occur even in man.