The work of Leeuwenhoek served to suspend for a time the subject of spontaneous generation, only to have it revived more vigorously later on. He is usually called “The Father of the Microscope,” though the compound microscope was invented probably by Hans Zansz or his son Zacharias, of Holland, about 1590. Leeuwenhoek used a simple lens, but his instruments were so much more powerful that they opened up an entirely new and unknown world. (Fig. 1.) Anthony van Leeuwenhoek (1632-1723) was apprenticed to a linen draper and accumulated a comfortable fortune in this business. He became interested in the grinding of spectacle lenses, then an important industry in Delft, Holland, where he lived, and did a great deal of experimental work in this line, mainly for his own enjoyment. Finally he succeeded in making a lens so powerful that he could see in water and various infusions very minute living bodies never before observed. Leeuwenhoek contributed 112 papers to the Royal Society of Great Britain, the first in 1673, many of them accompanied by such accurate descriptions and drawings, for example a paper submitted September 12, 1683, that there is no doubt that he really saw bacteria and was the first to do so (Fig. 2). Rightly may he be styled “The Father of Bacteriology,” if not of the microscope. He says in one paper: “With the greatest astonishment I observed that everywhere through the material I was examining were distributed _animalcules_ of the most microscopic dimness which moved themselves about in a remarkably energetic way.” Thus he considered these living objects to be animals, from their motion, and this belief held sway for nearly two hundred years. [Illustration: FIG. 1.--Leeuwenhoek’s Microscope. A is the simple bi-convex lens held firmly in place. In front of this is the small table, B, with the support, C, on the tip of which the object to be examined was held. This support could be brought nearer to or removed further away from the lens and held firmly in place by the screw, D. E is a second screw for raising or lowering the entire table. A concave mirror that Leeuwenhoek sometimes used to focus more light on the object under examination, is shown at the right.]