History of the microscope

Anton van Leeuwenhoek:
A history of the compound microscope

Anton van Leeuwenhoek (1632 - 1723) was a Dutch tradesman and scientist, best known for his work on the development and improvement of the microscope and also for his subsequent contribution towards the study of microbiology.


Using handcrafted microscopes, Anton van Leeuwenhoek was the first person to observe and describe single celled organisms, which he originally referred to as animalcules (which we now refer to as microorganisms). He was also the first to record and observe muscle fibres, bacteria, spermatozoa and blood flow in capillaries (small blood vessels).


Born in Delft, the Netherlands, on October 24, 1632, Anton van Leeuwenhoek (in Dutch Antonie van Leeuwenhoek) was the son of a basket maker. At the age of 16, van Leeuwenhoek secured an apprenticeship with a cloth merchant in Amsterdam as a bookkeeper and casher. There he saw his first simple microscope, a simple magnifying glass mounted on a small stand, as used by cloth merchants of the time. After a short period, had acquired one for his own use.


In 1654, van Leeuwenhoek returned to Delft where he started a own successful drapery business, though it was to be his interest in microscopes and a familiarity with glass processing that would lead to the significant discoveries he would later make.


The Father of Microbiology


Anton van Leeuwenhoek was an unlikely scientist, since he came from a family of tradesmen, had no fortune and received no higher education or university degrees. This would have been enough to exclude him from the scientific community completely, yet with skill and diligence, van Leeuwenhoek succeeded in making some of the most important discoveries in the history of biology, considered as "the Father of Microbiology".


And at some time before 1668, Anton van Leeuwenhoek had learned to grind lenses, making simple microscopes, which he used to make simple observations. Seemingly inspired to into more serious research after seeing a copy of Robert Hooke's illustrated book Micrographia, which depicted Hooke's own observations with the microscope and was very popular, van Leeuwenhoek started developing his own microscopes.


Van Leeuwenhoek's microscope


By placing the middle of a small rod of soda lime glass in a hot flame, van Leeuwenhoek could pull the hot section apart like taffy to create two long whiskers of glass. By then reinserting the end of one whisker into the flame, he could create a very small, high-quality glass sphere. These glass spheres then became the lenses of his microscopes, with the smallest spheres providing the highest magnifications.


Basic in design, van Leeuwenhoek's instruments consisted of simple powerful magnifying glasses, rather than the compound microscopes (microscopes using more than one lens) of the type used today or in Zacharias Jansen's original microscope design. Compared to a modern microscope, van Leeuwenhoek's design is extremely simple, using a single lens mounted in a tiny hole in a brass plate that makes up the body of the instrument. The specimen was then mounted on a sharp point that sticks up in front of the lens. Its position and focus could be adjusted by turning the two screws. The entire instrument was only 3-4 inches long, and had to be held up close to the eye, requiring good lighting and great patience to use.


Compound microscopes had been invented in the 1590s, nearly forty years before Leeuwenhoek was born, however there were technical difficulties in building them, meaning that early compound microscopes had a magnification of 20x or 30x. Yet although these early microscopes were much more similar in design to the modern microscopes of today, van Leeuwenhoek's simple magnifiers were able to achieve magnification of over 200x with to his skill in lens grinding, together with his naturally acute eyesight and great care in adjusting the lighting where he worked.


What further distinguished him was his curiosity to observe almost anything that could be placed under his lenses, and his care in describing what he saw. Although he himself could not draw well, he hired an illustrator to prepare drawings of the things he saw, to accompany his written descriptions.


Discovery of single-celled organisms


After developing his method for creating powerful lenses and applying them to a thorough study of the microscopic world, van Leeuwenhoek was introduced via correspondence to the Royal Society of London and soon began to send copies of his recorded microscopic observations. In 1673 his earliest observations of bee mouthparts and stings were published by the Royal Society. Despite this initial success, the Royal Society questioned van Leeuwenhoek's credibility when he sent the Royal Society a copy of his first observations of microscopic single-celled organisms. Previously, the existence of single-celled organisms were entirely unknown and initially were met with scepticism. Eventually, in the face of Van Leeuwenhoek's insistence, the Royal Society sent an team of respected observers to confirm van Leeuwenhoek's observations.


Van Leeuwenhoek's vindication resulted in his appointment as a Fellow of the Royal Society in that year. After his appointment to the Society, he wrote approximately 560 letters to the Society and other scientific institutions over a period of 50 years, detailing the subjects he had investigated.

Anton van Leeuwenhoek