is first alluded to in Greek writings by Theophrastus, about 315 B.C., but it was certainly known and used medicinally by the Chinese and in India long before. Apparently, too, it was known by the Egyptians. Dioscorides invented the name hydrargyrum, or fluid silver, for it. Pliny treats it as a dangerous poison. Galen adopted the opinion that the metal is poisonous, but states that he had no personal knowledge of its effects. With these authors argentum vivum was the term generally used to mean the native quicksilver, while hydrargyrum was more usually employed to describe the quicksilver obtained from the sulphide, cinnabar. Ancient writers appear to have regarded the two substances as distinct. Dioscorides points out that cinnabar was often confused with minium (red lead). The name Mercury, and the association of the metal (or demi-metal, as it was often regarded) with the planet and with its sign, formerly associated with tin, dates from the middle ages. It is mentioned first in this connection in a list of metals by Stephanus of Alexandria, in the seventh century. [Illustration] ARABS USED MERCURY MEDICINALLY. The Arabs, who inherited the medical lore of the Greeks, and probably added to this in the case of mercury knowledge acquired from India, were much interested in mercury. In the chemical works attributed to Geber not only the metal itself, but its compounds, red precipitate and corrosive sublimate, are described. Much use of mercury was made by the Arabs in the form of ointments for skin diseases, for which Mesuë recommended it, and Avicenna was probably the first physician to express doubt in regard to the poisonous nature of the metal. He observed that many persons had swallowed it without any bad effect, and he noted that it passed through the body unchanged. MERCURY PRESCRIBED INTERNALLY. Fallopius (1523-1562) remarks that in his time shepherds gave quicksilver to sheep and cattle to kill worms, and Brassavolus (1500-1554) states that he had given it to children in doses of from 2 to 20 grains, and had expelled worms by that means. Matthiolus (died 1577) relates that he had known women take a pound of it at a dose with the object of procuring abortion, and says it had not produced any bad result. FRICTIONS AND FUMIGATIONS.