Antoni van Leeuwenhoek Biography (1632-1723)

biologist, microscopist

Antoni van Leeuwenhoek is best remembered as the first person to study bacteria and "animalcules," or one-celled animals, now known as protozoa. Unlike his contemporaries Robert Hooke and Marcello Malpighi, Leeuwenhoek did not use the more advanced compound microscope; instead, he strove to manufacture magnifying lenses of unsurpassed power and clarity that would allow him tostudy the microcosm in far greater detail than any other scientist of his time.

Leeuwenhoek was born on October 24, 1632, in Delft, Holland. Although his family was relatively prosperous, he received little formal education. After completing grammar school in Delft, he moved to Amsterdam to work as a draper'sapprentice. In 1654, he returned to Delft to establish his own shop, and he worked as a draper for the rest of his life. In addition to his business, Leeuwenhoek was appointed to several positions within the city government, whichafforded him the financial security to spend a great deal of time and money in pursuit of his hobby--lens grinding. Lenses were an important tool in Leeuwenhoek's profession, since cloth merchants often used small lenses to inspecttheir products. His hobby soon turned to obsession, however, as he searchedfor more and more powerful lenses.

In 1671, Leeuwenhoek constructed his first simple microscope. It consisted ofa tiny lens that he had ground by hand from a globule of glass and placed within 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 hisown blood. He studied the structure of ivory as well as the physical composition of the flea, discovering that fleas, too, harbored parasites.

Leeuwenhoek began writing to the British Royal Society in 1673. At first, theSociety gave his letters little notice, thinking that such magnification from a single lens microscope could only be a hoax. However, in 1676, when he sent the Society the news that he had discovered tiny one-celled animals in rainwater, the interest of member scientists was piqued. Following Leeuwenhoek'sspecifications, they built microscopes of comparable magnitude and confirmedhis findings. In 1680, the Society unanimously elected Leeuwenhoek as a member.

Until this time, Leeuwenhoek had been operating in an informational vacuum; he read only Dutch and, consequently, was unable to learn from the published works of Hooke and Malpighi (though he often gleaned what he could from the illustrations within their texts). As a member of the Society, he was finally able to interact 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 hadreached near-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 objects could generate life. For example, it was believed that mold and maggots were createdspontaneously from decaying food. He succeeded in disproving spontaneous generation in 1683, when he discovered bacteria cells. These tiny organisms werenearly beyond the resolving power of even Leeuwenhoek's remarkable equipmentand 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 wrotenearly 200 letters that described his progress. However, he never divulged the method by which he illuminated his specimens for viewing, and the nature ofthat illumination is still a mystery. Upon his death on August 30, 1723, Leeuwenhoek willed twenty-six of his microscopes--a few of which survive in museums--to the British Royal Society.

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