Anton van leeuwenhoek timeline

Answer 1

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1674 - In a single vial of pond scum that he had taken from the Berkelse Mere, a small lake near Delft, he discovered and described the beautiful alga Spirogyra, and various ciliated and flagellated protozoa. Occasional prior observations by others notwithstanding, this singular event might justly be considered the simultaneous births of the fields of microbiology, protozoology (now called protistology) and phycology.

1674 - He found that yeast consists of individual plant-like organisms.

1675 - He discovered and accurately described and differentiated erythrocytes in humans, swine, fish and birds. We now know that the typical diameter of a human erythrocyte is 7.7 micrometers ("microns", µm). Using his sequential comparisons, van Leeuwenhoek calculated it to be "rather less than" 8.5 µm, a marvelously accurate result given his tools. He in fact expressed these dimensions in his usual manner by comparing sizes to sand grains. He observed that almost one hundred erythrocytes in a row would equal the diameter of a sand grain that he estimated to be the equivalent of 1/30 inch across. (The metric system was not to be introduced until 1791.) In 1683, he also described the sedimentation of red cells upon standing and their lysis on addition of fresh rain water, but not of sea water.

1677 - He was the first to observe spermatozoa in humans, dogs, swine, mollusks, amphibians, fish and birds. He often opined that this was his greatest find. At least at first, he thought that they were parasites in the male genitalia. The role of bulk semen in reproduction was already recognized. Sources conflict as to whether he ever guessed that fertilization occurs when one or more of these "animalcules" in semen enter the ovum. It might be noted that, other than his limner, his only known lab assistant was one Ludwig Hamm, who is cited as participating in this discovery. This mention may have been preserved so that posterity might not be forced to assume any unseemly behavior on Antonj's part.

1679 and 1684 - He described the needle-shaped microscopic crystals of sodium urate that form in the tissues of gout patients in stone-like deposits called "tophi". In 1684, he correctly guessed that much of the pain of gout is caused by these sharp crystals poking into adjacent tissues. More than a century would pass before any further advance in the understanding of gout.

1680 - He found and described foraminifera ("wee cockles") in the white cliffs of England's Gravesend and nematodes in pond water.

Between 1680 and 1701 he carried out many microdissections, mainly on insects, making an enormous number of discoveries:

He wrote extensive accounts of the mouthparts and stings of bees.

He was the first to realize that "fleas have fleas".

His keen perception enabled him to correctly conclude that each of the hundreds of facets of a fly's compound eye is in fact a separate eye with its own lens. This outlandish (but true) idea was met with derision by visiting scholars.

He discovered parthenogenesis ("virgin birth") in aphids, seeing that some parent aphids did not contain eggs, but fully formed young aphids. This tied in nicely with his belief in a preformationist theory of the nature of organic reproduction. (Charles Bonnet, 1720-1793,who later extensively studied and theorized about the implications of parthenogenesis, is often erroneously credited with its original discovery. He falsely claimed this honor to help his gaining admission as a corresponding member to the French Academy of Sciences in 1740, despite the fact that van Leeuwenhoek had died when Bonnet was three years old. - ed.)

1683 - In his most celebrated attainment, he discovered the bacteria in dental tartar, including a motile bacillus, selenomonads and amicrococcus.

1683 - He observed bacteria in feces, including a motile spirochete.

1683 - He found parasitic protozoa in feces (Giardia sp. and Balantidium sp.).

1683 - He saw the lymphatic capillaries, containing "a white fluid, like milk".

1698 - He described the blood capillaries in several species.

1702 - He observed the sessile ciliate protozoa Vorticella and Stentor, and the colonial protozoon Volvox in pond water, in which he followed and recorded daughter colony formation.

1702 - He discovered the diatoms, the bacillariophyta, in fresh water. As a rough gauge of the resolving power of his instruments, he was easily able to view and describe entire diatoms that are typically about 20-120 µm in length, but never noticed the characteristic pores in their frustules, which are usually somewhat less than 1 µm in diameter.

1702 - He viewed free-swimming and sessile rotifers in pond water. Some of these being just large enough to see with the unaided eye, others may have already noticed them, but his is the first published description. He was the first to describe the phenomenon ofanhydrobiosis (ability to survive desiccation) in a species of bdelloid ("leech-like", referring to their style of locomotion upon a surface) rotifer, Philodina roseola.

Philosopher and mathematician Gottfried Wilhelm Leibniz (1646-1716) wrote to van Leeuwenhoek in 1715 that "It would be well for young people to be introduced to microscopic observation, for which a school of microscopy should be founded." This wish went unfulfilled for a long time. The development of the microscope stagnated for almost a whole century. The introduction of the improved achromatic objectivelenses of Georg Plössl in the early 19th Century and the application by Ernst Abbe and Carl Zeiss of the Abbe Sine Condition in about 1860 finally brought the needed breakthroughs in the development of light microscopes with reasonably flat fields of view and minimal chromatic and spherical aberration. This development continues today at the major microscope manufacturers.

Antonj van Leeuwenhoek enjoys a rare distinction among revolutionary discoverers, in that he was widely recognized and honored for his genius in his own time. In 1716, when he was in his 84th year, the University of Louvain officially honored him by striking a gold medal with his likeness on the obverse and a view of the city of Delft on the reverse, in recognition of his work. A distinguished delegation from the university ceremoniously presented this to him in a bag made of woven gold bullion, along with a diploma. This incident corresponds roughly with the modern conferring of an honorary degree.

He died on 30th August, 1723, aged almost 91. He was interred at De Oude Kerk in Delft. His honorable status in the city entitled him to eighteen pallbearers.

In 1877, the Royal Society established the Leeuwenhoek Medal, awarded once each decade to the person judged to have made the most significant contributions to the field of Microbiology. Recipients have included such luminaries as Louis Pasteur (1895), Martinus Beijerinck(1905) and Sergei Winogradsky (1935).