What Did Zacharias Janssen Contribute to Microbiology?

The discipline of microbiology would not exist, or would be a much smaller branch of science, without the microscope. While modern microscopy includes specialized microscopes that can use ultraviolet or infrared light, holographic microscopes or even laser microscopes, the originator of the microscope used primitive lenses to open up a whole new world for exploration. Zacharias Janssen, along with his father Hans, played a large part in that revolution.

Zacharias Janssen was a spectacle maker in the late 16th and early 17th century. He is credited with making the earliest compound microscope in the 1590s. While Zacharias is credited with the invention of the microscope, as well as the telescope, the invention is dated to his teenage years, so it is likely that his father played a role. The first microscope was a tube with a lens in each end, mounted on a tripod. It could magnify objects five to nine times.

A modern compound microscope often has two eyepieces, or oculars, with one lens each so that you can have binocular vision. A prism at the juncture of the oculars with the body splits the image for each side. There are generally three to four objective lenses at the other end of the microscope body, allowing for magnifications between 10 and 100 times the magnification of the ocular lenses for a total of 100 to 1000 times magnification. The microscope is mounted on a stand, the specimen sits on a stage and a light source illuminates the field.

Ancient Romans had a rudimentary germ theory, but the history of microbiology really starts with the microscope. Using the microscope, Robert Hooke made the first observations of microscopic phenomena and Anton van Leeuwenhoek recorded single celled organisms including bacteria, protozoa and fungi. The microscope was used to find the causative agents of plant and animal diseases. It was instrumental in discovering the variety and function of the whole invisible microscopic world.

The Janssens were the first to create a compound microscope, but their invention ushered in a century of rapid advancement in the technology. Other inventors who created versions of a compound microscope include Hans Lippershey, Galileo Galilei, Cornelius Drebbel and Christiaan Huygens. Carl Zeiss significantly improved the design of the compound microscope in the 19th century. Ernest Abe introduced the oil immersion lens soon after, improving the clarity of high magnification images.