A fabric merchant and self-made scientist, Antonie (Anthony) van Leeuwenhoek had boundless curiosity and an open mind, free of scientific dogma. Although he is often mistakenly credited with invention of the microscope, his improvements to the instrument, and subsequent observations, made him one of the most important figures in the history of microbiology.
* Leeuwenhoek's Lenses *
A Dutch tradesman from Delft, Netherlands, Leeuwenhoek did not pursue higher education. At age sixteen, he became apprentice to a Scottish cloth merchant in Amsterdam, and eventually moved back to Delft, where he hung out his own shingle as a draper. A perfectionist in all respects, Leeuwenhoek was not satisfied using available lenses to examine his fabrics, so he learned to grind his own.
Crafting lenses was the first step towards Leeuwenhoek's contributions to microscopy. Historians believe that he was inspired to take up the microscope after reading Robert Hooke's popular illustrated book "Micrographia", which depicted Hooke's own observations with the primitive, and limited, microscopes of the time (Dobell 1960).
* Hand-Crafted Microscopes *
Leeuwenhoek constructed more than 500 of his own microscopes, although fewer than ten survive to this day. These instruments were not the modern, compound microscopes that we are familiar with, but instead were very simple, powerful magnifying glasses.
A single lens was inserted into a tiny hole drilled in a small brass plate. The specimen was mounted on a sharp point in front of the lens; its position and focus adjusted by turning two screws. The instrument was no more than four inches long and had to be held very close to the eye. Using Leeuwenhoek's microscope required good lighting and much patience.
Although, Leeuwenhoek is often referred to as the inventor of the microscope, more complex, compound microscopes had been invented nearly forty years before he was born, and had already been used to make important discoveries (Ford 1991). But early compound microscopes had limitations. They could not effectively magnify objects more than thirty times natural size.
* Leeuwenhoek Increased Magnification *
Leeuwenhoek's simple microscopes magnified objects to over 200 times actual size, with clearer and brighter images than any of his predecessors had achieved. It is even suspected that van Leeuwenhoek created some microscopes that could magnify up to 500 times, although none of those scopes are known to have survived to date (Dobbell 1960).
* Animalcules *
Leeuwenhoek was also distinguished by an insatiable curiosity to observe just about anything that would fit under his lenses, and he made careful, detailed observations of whatever he saw. Through these observations, he succeeded in making some of the most important discoveries in the history of biology.
He discovered microscopic organisms (such as bacteria, protists, nematodes, rotifers), which he dubbed "animalcules", as well as sperm cells, blood cells, and muscle fibers. Leeuwenhoek's discovery of microorganisms, along with experiments done by Francesco Redi, Lazzaro Spallanzani and Louis Pasteur, helped put to rest the erroneous belief in spontaneous generation (living things commonly arising from nonliving matter) (Dobell 1960).
* Induction Into the Royal Society *
After twenty years of careful observation, Leeuwenhoek revealed his findings to the Royal Society of London. His important research, which was widely circulated, exposed the existence of a vast array of microscopic life to the scientific community. Although Leeuwenhoek had no formal scientific training, the astounding and detailed nature of his observations resulted in his induction as a full member of the Royal Society in 1680, where he joined the ranks of many other scientific luminaries of his day.
* Leeuwenhoek's Secrets *
Although his findings were well-known, Leeuwenhoek was very secretive about how his microscopes were constructed, including the critical secret of how he crafted his lenses. He died in 1723, taking many mysteries of his genius with him to the grave (Ford 1991).
* Sources *
Dobell, C. (ed.) 1960. Antony van Leeuwenhoek and his "Little Animals." Dover Publications, New York.
Ford, B. J. 1991. The Leeuwenhoek Legacy. Biopress, Bristol, and Farrand Press, London.