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Antony van Leeuwenhoek. (A Portrait in History).

Antony van Leeuwenhoek was one of the greatest innovators in the world of biological sciences. Driven by insatiable curiosity and infinite energy, Leeuwenhoek devoted some 50 years of his life to his all-consuming passion--microscopy. He relied on his own innate genius in his lifelong quest to uncover the marvels of Nature.

Leeuwenhoek (1632-1723) was born on October 24, 1632, in Delft, Netherlands. His father was a basket weaver Leeuwenhoek received no formal schooling in medical or biological sciences. He established a successful drapery business in Delft. Being in the cloth trade, he might have become familiar with the use of a magnifying glass for inspecting fiber quality and determining weaving type. Leeuwenhoek did not pursue what would become his favorite hobby, microscopy, until he was almost 40.

In 1660, Leeuwenhoek was nominated as chamberlain to the Sheriffs of Delft. Later, he also worked as a surveyor and wine gauger. His official duties were not that cumbersome, which allowed him time to pursue his hobby of constructing microscopes and viewing everything under his lens. His approach to microscopy was thorough, systematic, and analytical. For 50 years, he painstakingly recorded his many observations in a series of letters to the Royal Society of London. These letters were published in the Philosophical Transactions of the Royal Society.

Leeuwenhoek's subjects for microscopy were extremely diverse and included objects from the human, animal, plant, and mineral kingdoms. He examined tartar of teeth, saliva, gum scrapings, hair, nails, bones, teeth, various soft tissues, and the lens of the eye, as well as various biological fluids, including blood, milk, sweat, and tears. Other subjects of his studies included feathers, animal fur, insect parts, minerals, fish scales, spices, nuts, seeds, tree bark, and cork. Leeuwenhoek provided accurate descriptions of plant anatomy. Even gunpowder, before and after being ignited, came under his microscopic scrutiny. He used saffron as a means to render tissues such as muscle more easily visible, and he also described blood corpuscles and capillaries.

An expert lens maker, Leeuwenhoek ground and polished his own lenses. He used a simple microscope, although compound microscopes were available at the time. He prepared sections with the aid of a razor and cut them with his own hand. For sketches and illustrations accompanying his written observations, he sought the services of a draftsman.

Leeuwenhoek did not write in English or Latin and spoke only Dutch. It was Reijnier de Graaf who wrote to the Royal Society in 1673 informing them of Leeuwenhoek, describing him as the resident genius of Delft who devised remarkable microscopes. Graaf's efforts introduced Leeuwenhoek to the most important learned society of the time. Accompanying Graaf's introductory note was the first letter to the Royal Society written by Leeuwenhoek, which dealt with observations on the structure of mold, as well as the structure of the bee and the louse. This note launched Leeuwenhoek's entry into the nascent world of microscopy.

Leeuwenhoek gave detailed descriptions of protozoa and bacteria. He noted that "little animals" lived in all kinds of water--lakes, wells, canals, and even rain. His first observations on free living protozoa probably began with his discovery of little animals, or "animalcules," in fresh water from a lake, which he recorded in a 1674 letter to the secretary of the Royal Society, Henry Oldenburg. Leeuwenhoek's celebrated letter of October 9, 1676, contained the first account ever written of bacteria and outlined his pepper water experiment. In April 1676, in what might have been an attempt to discover "the cause of the hotness or power whereby pepper affects the tongue," Leeuwenhoek placed some pepper in water Three weeks later, on April 24, 1676, he discovered an incredible number of very little animalcules, marking the first sighting of bacteria. Robert Hooke repeated the pepper water experiment and confirmed Leeuwenhoek's observations. The Fellows of the Royal Society also got a glimpse of "great numbers of exceedingly small animals swimming to and fro." In 1683, Leeuwenhoek presented another famous communication on bacteria found in saliva and tooth scrapings from his mouth.

It is one of the miracles of science that 2 men from the town of Delft would make pioneering contributions to the problem of generation and reproduction. Reijnier de Graaf, also of Delft, discovered the ovarian follicles named after him. Leeuwenhoek made groundbreaking observations in andrology by describing spermatozoa. A medical student, Johan Ham, was the first to see animalcules (spermatozoa) in human semen, and he drew this to Leeuwenhoek's attention. Leeuwenhoek credited Ham with the discovery in his letter of November 1677. Leeuwenhoek went on to document the presence of animalcules in other species. He was one of the strongest opponents of the doctrine of spontaneous generation in the 17th century.

This pioneer microscopist revealed little information on how he perfected his lenses and his "particular manner of observing very small creatures." The magnifications achieved with his lenses ranged between x 30 and x 200, with one lens estimated to have a magnification of x 270 and a resolving power of 1.4 [micro] m. It is believed that Leeuwenhoek might have attained even higher magnifications. He used a special technique for viewing and lighting his objects, which he never divulged. It has been suggested that Leeuwenhoek might have used some simple means of dark-field illumination to visualize details such as flagella on bacteria. Before the invention of the micrometer, it was difficult to measure the size of small objects under the microscope. Leeuwenhoek tried ingenious ways to estimate the size of his animalcules. Some themes he used for size comparison included grains of sand, a human red blood corpuscle, the millet seed, and "a hair's breadth."

Leeuwenhoek neither lectured nor wrote formal scientific papers but rather presented his observations in his letters. Nevertheless, he was recognized as an original scientist and was admitted as a fellow to the Royal Society. Leeuwenhoek was visited by many celebrities of his time, including royalty.

The leading microscopist of Delft died on August 26, 1723, at the age of 90. His contributions to science have been well documented by several authors, most notably by the late Clifford Dobell in his captivating book, Antony van Leeuwenhoek and His Little Animals. In addition to the 26 microscopes and preparations he bequeathed to the Royal Society, Leeuwenhoek left behind a large collection of microscopes and mounted lenses, which were auctioned 2 years after his daughter Maria died. It is believed that Leeuwenhoek made more than 500 microscopes or mounted lenses. Leeuwenhoek was one of the most curious and original men who ever lived--he saw what had never been seen before. The medical world continues to be in awe of this extraordinary genius who unveiled the mysteries of Nature under the microscope.

Accepted for publication January 28, 2002.

From the Division of Pathology, The Hospital for Sick Children, Toronto, Ontario, Canada.

The author acknowledges that the general biographical overview presented does not necessarily include all of the accomplishments or achievements associated with the person discussed. Dr Jay welcomes comments from readers concerning the "A Portrait in History" section.

Reprints not available from the author.
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Title Annotation:microscopist
Author:Jay, Venita
Publication:Archives of Pathology & Laboratory Medicine
Article Type:Biography
Geographic Code:4EUNE
Date:Jun 1, 2002
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