Leeuwenhoek, Antoni van

Antoni van Leeuwenhoek (1632-1723) is best remembered as the first person to study bacteria and one-celled animals now known as protozoa. Unlike his contemporaries, Leeuwenhoek did not use the more advanced compound microscope. Instead, he tried to manufacture magnifying lenses of great power and clarity that would allow him to study micro-coorganisms in far greater detail than any other scientist of his time.

Early Career

Although Leeuwenhoek's family was fairly well off, he received little formal education. After completing grammar school in Delft, Netherlands, he moved to Amsterdam to work as a draper's apprentice (a draper was a person who made and sold clothing). In 1654 he returned to Delft to establish his own shop and worked as a draper for the rest of his life. His medical achievements in lens grinding were actually a hobby rather than his main work. Lenses were an important tool in Leeuwenhoek's profession, since cloth merchants often used small lenses to inspect their products. His hobby soon turned to obsession, however, as he searched for more and more powerful lenses.

In 1671 Leeuwenhoek made his first simple microscope. It had a tiny lens that he had ground by hand from a globule (small ball) of glass and had placed in a brass holder. To this he had attached a series of pins designed to hold the specimen. It was the first of nearly six hundred lenses ranging from 50 to 500 times magnifications that he would grind during his lifetime.

Through his microscope Leeuwenhoek examined such substances as skin, hair, and his own blood. He studied the structure of ivory as well as the physical composition of the flea, discovering that fleas, too, had even smaller parasites on them.

Leeuwenhoek began writing to the British Royal Society in 1673 about his discoveries. At first, the Society gave his letters little notice, thinking that such magnification from a single lens microscope could only be a hoax (fake). The best microscopes had more than one lens to provide better clarity. In 1676, when he sent the Society the news that he had discovered tiny one-celled animals in rainwater, scientists became interested in his work. Following Leeuwenhoek's instructions, they built microscopes of comparable magnitude and confirmed his findings. In 1680 the Society unanimously elected Leeuwenhoek as a member.

Further Research

Until this time, Leeuwenhoek had been operating without any information on what other microscope developers were doing. He read only in Dutch and was unable to learn from the published works of Hooke and Malpighi, the other great microscopists of the time. As a member of the Royal Society, however, he was finally able to correspond with other scientists. In fact, the news of his discoveries spread worldwide, and he was often visited by royalty from England, Prussia, and Russia. The traffic through his laboratory was so persistent that he eventually allowed visitors by appointment only. Near the end of his life he had reached legendary status, and was often referred to by the local townsfolk as a magician.

Amid all the attention, Leeuwenhoek remained focused upon his scientific research. Specifically, he was interested in disproving the common belief in spontaneous generation, a theory proposing that certain inanimate (non-living) objects could generate life. For example, it was believed that mold and maggots were created spontaneously from decaying food. He succeeded in disproving spontaneous generation in 1683 when he discovered bacteria cells. These tiny organisms were nearly beyond the resolving power of even Leeuwenhoek's remarkable equipment and would not be seen again for more than a century.

Leeuwenhoek created and improved upon new lenses for most of his long life. For the forty-three years that he was a member of the Royal Society, he wrote nearly 200 letters that described his progress. However, he never wrote about the method he used to light up his specimens for viewing, and the nature of that lighting technique is still a mystery. Upon his death, Leeuwenhoek willed twenty-six of his microscopes—a few of which survive in museums—to the British Royal Society.