In the seventeenth century, also, zoology and botany were largely extended. In it lived Swammerdam (1637-1680), famous as a naturalist, physiologist, linguist, poet, and _savant_; there were others, also, whose names are better known in the history of collateral science than in medicine, and who left conclusive demonstrations in accordance with their theories, and made daily use of the microscope, simple as it then was. The term "cell" had been introduced by Hooke in 1667, and Malpighi and Grew were the founders of the cell-doctrine. The astronomical laws discovered by Copernicus changed the course of the world's thought; and now appeared the brilliant Kepler (1571-1630), and Galileo (15641642), the defender of the Copernican system, and the persecuted discoverer of the law of falling bodies, of the thermometer, the telescope, and the movements of Jupiter; also, Sir Isaac Newton (1642-1727), whose discovery of the laws of gravitation in 1665 marked an era in the history of science. This century, too, gave birth to Romer, who in 1675 calculated the velocity of light; Huyghens (1627-1693), who discovered the polarization of light and the satellites of Saturn; James Gregory, who in 1663 made{154} a reflecting telescope with a metallic concave mirror; Torricelli, who in 1643 measured the weight of the air; Gascoigne, who invented the micrometer in 1639; and Napier, who invented logarithms in 1700. Now chemistry, having ceased to be alchemy, began to don the dignity of a science _per se_, and it may be claimed that medicine derived no slight benefit therefrom. Scientific societies and journals arose at this period, and were all of good service to medicine in their way. The church scented danger to the faith in everything which related to natural science, and founded certain secret associations, especially in Italy; the Accademia Degli Lyncei, so called from its seal, which bore the image of a fox or lynx, founded in Rome in 1603, was one of these. Counter-societies, or, rather, societies with opposite purposes, were also started, and the original and private so-called Invisible Society, which was originated mainly by Milton, in 1645, and remodeled by Charles II in 1662, is now the flourishing Royal Society. In France the Academy was founded in 1665 by Colbert, but developed its first real activity thirty-five years later.