Monstrosities have attracted notice from the earliest time, and many of the ancient philosophers made references to them. In mythology we read of Centaurs, impossible beings who had the body and extremities of a beast; the Cyclops, possessed of one enormous eye; or their parallels in Egyptian myths, the men with pectoral eyes,--the creatures "whose heads do beneath their shoulders grow;" and the Fauns, those sylvan deities whose lower extremities bore resemblance to those of a goat. Monsters possessed of two or more heads or double bodies are found in the legends and fairy tales of every nation. Hippocrates, his precursors, Empedocles and Democritus, and Pliny, Aristotle, and Galen, have all described monsters, although in extravagant and ridiculous language. Ballantyne remarks that the occasional occurrence of double monsters was a fact known to the Hippocratic school, and is indicated by a passage in De morbis muliebribus, in which it is said that labor is gravely interfered with when the infant is dead or apoplectic or double. There is also a reference to monochorionic twins (which are by modern teratologists regarded as monstrosities) in the treatise De Superfoetatione, in which it is stated that "a woman, pregnant with twins, gives birth to them both at the same time, just as she has conceived them; the two infants are in a single chorion." Ancient Explanations of Monstrosities.--From the time of Galen to the sixteenth century many incredible reports of monsters are seen in medical literature, but without a semblance of scientific truth. There has been little improvement in the mode of explanation of monstrous births until the present century, while in the Middle Ages the superstitions were more ludicrous and observers more ignorant than before the time of Galen. In his able article on the teratologic records of Chaldea, Ballantyne makes the following trite statements: "Credulity and superstition have never been the peculiar possession of the lower types of civilization only, and the special beliefs that have gathered round the occurrence of teratologic phenomena have been common to the cultured Greek and Roman of the past, the ignorant peasant of modern times, and the savage tribes of all ages. Classical writings, the literature of the Middle Ages, and the popular beliefs of the present day all contain views concerning teratologic subjects which so closely resemble those of the Chaldean magi as to be indistinguishable from them. Indeed, such works as those of Obsequens, Lycosthenes, Licetus, and Ambroise Pare only repeat, but with less accuracy of description and with greater freedom of imagination, the beliefs of ancient Babylon. Even at the present time the most impossible cases of so-called 'maternal impressions' are widely scattered through medical literature; and it is not very long since I received a letter from a distinguished member of the profession asking me whether, in my