Antoni van Leeuwenhoek

Antoine van Leeuwenhoek (or Antoni or Anthonie ) (October 24th 1632, Delft - August 27th 1723, Delft) is commercial and erudite a Dutch.

Van Leeuwenhoek is especially known for its improvements of the Microscope and as one of the precursors of what one will call later the cellular Biologie and the Microbiologie. It thus continued the work of Jan Swammerdam (1637-1680) which lived with Amsterdam. It is a little by chance that it is the first to make astonishing observations with a Microscope of its manufacture. Become corresponding of the Royal Society of London, he becomes member in 1680 about it. From 1674 with its death it makes many discoveries.

Biography

Leeuwenhoek, wire and grandson of one manufacturing of basket, are baptized with the Protestant reformed church. His/her father dies when it was still very young and his mother remarie in 1637. In 1648, he becomes apprentice in a clothier of Amsterdam. After its training, it occupies the functions of accountant and cash clerk in his Master. In 1656, it goes back to Delft: it there Marie and opens a shop of clothier and of drapery but one knows only few things of his marketing activities.

Five years after the death of its first wife, it remarie in 1671. His second wife dies in 1694 letting Leeuwenhoek only deal with sound only child, her Maria daughter, only surviving of her five children.

In 1660, it obtains the function of chamberlain from the judges of Delft. In 1669, he becomes “geometrician”, in 1679, Leeuwenhoek becomes “wine gauge” and, finally, as from 1677, he also occupies the function of managing director of the district of Delft. These various stations indicate the prosperous position of Leeuwenhoek in the city. It seems that he separates from his trade of drapery shortly after 1660 because its correspondence does not make null mention of it. Its municipal employment leaves him, seems it, a considerable time for the Microscopie.

Its finances are good the more so as he inherits a house the family of his first wife. In 1666, it buys a garden outside the city and in 1681, it has a horse. An indication of its fortune is given by the heritage which leaves his/her daughter, Maria, with her death, in 1745 and which represents 90.000 Guineas, a considerable sum for the time. However, certain authors note that Leeuwenhoek “occupied a modest municipal employment until its death”.

Constantijn Huygens (1596-1687) will say: “You voijez as this good Leeuwenhoeck is not wearied to excavate everywhere where its microscopy can arriuer, so much of others more sçauans vouloijent to take the mesme sorrow, the descouverte beautiful things iroit bientost more loing”. If these observations cause the amazement of the scientists of its time, one will reproach him later, his lack of scientific knowledge which the fact accentuates that he does not know any foreign language. This absence of knowledge enabled him to carry out its observations of a new eye, without the prejudices of the anatomists of its time. It leaves an only consigned immense work letters, approximately 300, all written in Dutch and the majority sent to Royal Society. He writes, in a letter with Henry Oldenburg dated October 30th, 1676, whom he hopes to receive from his correspondents of the objections to his observations and whom he commits himself correcting his errors. He answers besides the first marks of skepticism marking the publication of his observations by an obvious self-confidence. Its observations will be sufficiently famous to receive many distinguished visitors like the queen Marie II of England (1662-1694), Pierre Large the (1672-1725), Frederic I {{er}} of Prussia (1657-1713), but also of the philosophers and the scientists, the doctors and the men of the church, etc Leeuwenhoek carries out in front of them many demonstrations. It remarks in Pierre Large blood circulation in the tail of an eel.

Its microscopic observations: a new field of knowledge opens

One is unaware of why Leeuwenhoek starts to use a microscope. It is the Dutch doctor and anatomist Reinier de Graaf (1641-1673) which presents its first observations to the Royal Society in 1673: Leeuwenhoek describes the structure of mould and the pivot of the bee. Then begin an intense exchange of letters in Leeuwenhoek - in which he consigns, lasting nearly forty years, its observations - and the members of the London learned society, exchange which will continue until the death of Leeuwenhoek in 1723. Royal Society admits it in its center in 1680 and the Academy of Science of Paris admits it like member corresponding in 1699.

Leeuwenhoek makes its observations on simple microscopes that it carries out itself. It bequeaths, with its death, 26 microscopes in Royal Society which were never used and, one century later, were already lost. Two after the death of his/her daughter, Maria, a batch of more than 350 of its microscopes as 419 lenses are sold on May 29th, 1747. 247 microscopes were complete, often with the last object still observed in place. Two of these instruments comprised two lenses and only one had three of them.

The best of its apparatuses can agrendir 200 times. It does not leave any indication on its manufacture of the lenses and it will be necessary to wait several decades to have so powerful apparatuses again. One is unaware of how it lit the objects observed thus that their power. Most powerful of its instruments preserved today has a rate of enlarging of 275 times and a resolution of 1,4 μm. If the weather is present of several of its microscopes at its close relations, it never sells only one of them. One estimates at only one ten the microscopes which it manufactured today preserved.

The discovery of the protozoa

One is unaware of when it starts to observe Bactérie S and others Micro-organisme S. It is in a letter dated September 7th, 1674 that it evokes for the first time of the tiny forms of life which it observed in water of a lake near Delft. After having announced again these creatures in two letters of December 20th, 1675 then of January 22nd, 1676, it is in a long letter of seventeen layers, dated October 9th, 1676, that it describes what we name today of the Protozoaire S, especially of the Cilié S with which mix with the Algue S ( Euglena and Volvox ).

It thus will describe many organizations whose determination is more or less possible today: Vorticella campanula , Oicomonas termo, Oxytricha sp. , Stylonychia sp., Enchelys, Vaginicola, Coleps . But these observations are received with skepticism by the scientists of the time, also, Leeuwenhoek joint with another letter (October 5th, 1677), the testimony of eight people, pastors, lawyer, doctor, gunner with the arc affirming to have seen many and are varied living beings. It also receives the support of Robert Hooke (1635-1703) which, at the time of the meeting of November 15th, 1677 of Royal Society, the reality of the observations of Leeuwenhoek shows. The translator of the letters which appear in the Philosophical Transactions , the publication of Royal Society, name them animalcula .

Leeuwenhoek joint with a letter of June 1st, 1674 addressed to the secretary of Royal Society, Henry Oldenburg (v. 1618-1677), samples of the organizations which it had observed.

Leeuwenhoek is an adversary of the theses on the spontaneous Generation. When he discovers the animalcules, he thinks that they are formed thanks to “fortuitous segregation of the particles of water” but he rejects this explanation by affirming that these animalcules or their seeds preexist in rainwater. He learns, a few years later, that Italian Francesco Redi (1626-1697) could prove that the flies did not reproduce by spontaneous generation: Redi uses closed tubes in which it locks up meat in decomposition. No fly appears in these tubes while others, nonclosed and left with the free air, give to maggots then flies. For Redi, the appearance of flies depends on adults who will lay in the meat. Leeuwenhoek tries to reproduce this experiment, but the conditions are not perfect and it notes the presence of animalcules even if the tubes containing water is locked up in a sealed tube.

The discovery of the spermatozoa

It is in 1677 qu' it mentions for the first, in a letter addressed to Royal Society, very many animalcules in sperm.

Leeuwenhoek did everything conscience that its observations which show that the seed contained in the Testicule S is at the origin of the reproduction of the mammals will run up against the scientific consensus of its time. Because its observations make against the theses developed by large scientists of the time like William Harvey (1578-1657) or Reinier de Graaf (1641-1673).

Leeuwenhoek and the spontaneous generation

One often retains the name of the Dutch scientist as one of those which are opposed, at the 17th century with the theory of the spontaneous generation. We above evoked work of Francesco Redi (1626-1697). Another Dutch, Jan Swammerdam (1637-1680), made many observations on the insects and their reproduction.

Leeuwenhoek does not seem to be opposed to the theory of the spontaneous generation at the beginning of its observations. Thus, he studies in the middle of the years 1670, he dissects Pou X and observes small lice in eggs being in the body of the females. He makes similar experiments on the Puce S and their eggs (which he preserves until maturity), but does not manage to recognize in the larvae the chips and this in spite of the observations of Swammerdam published a few years earlier. He will return a few years later on these animals.

Being interested, at the beginning of 1679, with the presence of worm ( Fasciola hepatica ) in the liver of sheep, like Redi and Swammerdam, it does not include/understand the life cycle of the animal complexes which will be elucidated only well later.

Its other observations

The interest of Leeuwenhoek goes on very varied objects and does not seem to follow a prédifini plan. Its observations in zoology are numerous.

Leeuwenhoek observes that the Anguillule of the vinegar ( Anguillula aceti ) is Vivipare, which confirms its opposition to the theory of the spontaneous Generation.

He studies the red Globules of many animals and the human being as well as the network blood (capillaries) of the tail of the Têtard, of the foot of the Grenouille S, the caudal fin of the Anguille and the wing of the Chauves-souris.

Leeuwenhoek describes the structure of various the Phanère S: Feather S of several of Bird X, hairs or fur of bear, the fish scales.

Like the other microscopic ones of its time, he studies the anatomy of many insects like bees, midges, chips, bugs, worms with silk. He is the first to observe the difference in postures of the larvae of mosquitos ( Culex and Anopheles ).

In botany, he studies the structure of the sheets and the wood of various species. It is interested in the relation between the structure of various spices and their taste (coffee, pepper, the, nutmeg, ginger, sage…

All the observations of Leeuwenhoek are not devoted to objects of the alive world. Thus he studies and describes the Gunpowder before and after his combustion. He studies in the same way the structure of various metals as well as rocks, crystals, salts…

Leeuwenhoek, in a letter dated April 25th, 1679, gives the first estimate of the maximum population which the Ground could carry. It is based on the density of Holland at its time (120 people per square kilometer) and estimates that the Earth could accommodate 13,4 billion human beings.

The judgment of the historians

Julius von Sachs (1832-1897) in its history of botany says that “all this work of botany is marked with the corner of a surface nature which testifies to purely accidental and momentary occupations; the interest which it tested for the problems of the philosophy of the nature which reigned at the time about which we speak, for those in particular who touch with the field of the theory of the evolution, pure curiosity and the desire to tackle mysterious questions, inaccessible to the commun run, led Leeuwenhoek to undertake the studies about which we spoke. But it could not coordinate the results of its observations so as to have an exact idea of the vegetable structure as a whole. ”. Sachs recognizes nevertheless the quality of the observations of Leeuwenhoek which shows, according to him, the great power of the lenses carried out by the Dutch scientist.

For Julius Victor Carus (1823-1903) in his history of the zoology: “It was in some fate the first of these amateurs who request from the microscope only one quiet recreation. There are almost no anatomical systems that Leuwenhœck did not enrich by important facts”. For Carus, “One hardly made progress since him until O. - F. Muller”.

Leeuwenhoek medal

Its name was given to the Médaille Leeuwenhoek allotted by the royal Académie of arts and sciences Dutchwoman since 1877 and rewarding work for a microbiologist.

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