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Medicine, on its march through millennia, many times has been the beneficiary of
men who, uninhibited by the mores of formal education, have allowed their curiosities
free rein and have followed leads to basic discoveries that had eluded professional
practitioners for centuries. By unorthodox methods, frequently scorned as unscientific,
it has been their God-given privilege to come upon revelations that have been boons
to all mankind through advancement of the healing arts. Such a man was Antony van
Leeuwenhoek.
Leeuwenhoek was not the inventor of the microscope, although it often has been credited
to him erroneously. But there is no question that he deserves to be called the father
of microscopy, and credited as the man who laid foundations for the sciences of
bacteriology and protozoology. With tiny lenses laboriously ground by his own secret
methods, Leeuwenhoek became the first man to observe and to report on fascinating,
multifarious microscope forms of life with which, though unbeknown to him, man had
coexisted for untold centuries.
Antony van Leeuwenhoek was born at Delft, Holland, and October 24, 1632. His father
was a basket maker, and died when Antony was five years, he was sent to a linen
draper’s shop in Amsterdam to learn the business.
After six years in Amsterdam, Leeuwenhoek returned to his native town. Shortly thereafter,
Leeuwenhoek married, bought a house and shop, and set himself up in business as
a draper and haberdasher.
In addition to his drapery business, Leeuwenhoek enjoyed considerable civic success.
He held a municipal office comparable to that of alderman; he was official wine-gauger;
and he was licensed as a surveyor.
There seems to be no record of how or when Leeuwenhoek became interested in grinding
lenses and using them to investigate objects too small to be seen by the naked eye.
Noris it clear how he learned the art of lens-grinding. Throughout his life he kept
his technical methods secret. Within the confines of his “closet,” as
he called his workroom, he turned out hundreds of tiny lenses, and mounted them
laboriously but crudely between two thin sheets of silver or brass with small openings
masking all but the central are of the lens. Most of his instruments were but two
to three inches in height, an inch or less in width, and, except for thumbscrews,
less than a half inch in depth. Solid specimens were mounted before the lenses on
needle points, adjustable with thumbscrews both for height and for distance. Other
microscopes were designed to hold small glass vials, or capillary tubes, to bring
liquids within extremely short focal ranges. All of Leeuwenhoek’s microscopes
were made with single lenses; he used no compound lenses. By variations of grinding,
he secured lenses of various magnifications. Most of them had magnification factors
of not more than 160 diameters, although one in the collection at Utrecht University
Museum is reported to magnify 275 diameters The first report of Leeuwenhoek’s
activity in this new and fascinating field came in 1673, when his good friend and
fellow-townsman, the famed physician Reinier de Graaf, wrote to the secretary of
the Royal Society of London, describing Leeuwenhoek’s work and enclosing a
letter from the microscopist. This letter was the first of no less than 375 communications
written by Leeuwenhoek to the society over a 50-year period. Evidently Fellows of
the Royal Society liked the reports on Leeuwenhoek’s observations, for the
secretary, Henry Oldenburg, encouraged him to continue his correspondence.
Leeuwenhoek’s letter forms a unique contribution to the literature of science
and particularly of medicine. They were nearly all written in Dutch, the only language
he knew; and in a simple, native, conversational style- sometimes frank and earthy.
A native honesty ran through them, however; while Leeuwenhoek’s untutored
and unscientific interpretations of what he was most careful to distinguish between
descriptions of things he actually saw, and those he conjectured or “imagined.”
He was so intent on telling what he had seen or thought that he had no time to worry
about grammar or niceties of literary composition. He worked entirely by himself,
receiving no help from contemporary microscopists. He disliked and resented interference,
and he distrusted the knowledge- and sometimes the purpose- of persons who went
to see him or offered him advice.
In 1680, Leeuwenhoek was elected a Fellow of the Royal Society- a distinct honor
and recognition for one living outside England. In 1699, the Academie des Sciences
of Paris elected him a correspondent. His observation excited great interest, and
were widely read- but that was all. Nobody seriously attempted to reappear or to
extend them. As the seventeenth century closed, Leeuwenhoek was the only earnest
microscopist then living in the world.
Leeuwenhoek’s specimen came from his everyday surroundings. No material or
substance escaped the insatiable curiosity of the draper of Delft: rain water, scum
from the surface of ponds, infusions of peppercorns, unborn mussels, animal and
human tissues, scrapings, excreta of all sorts, and all kinds of mineral and vegetable
matter, all came before his lenses.
Notable among Leeuwenhoek’s peculiar habits was this practice: when he found
a specimen particularly to his linking, he left it attached to the microscope and
made another instrument. Over the years he accumulated many of these. He placed
these in pairs in small lacquered boxes, 12 to 24 boxes in a case. One such case
he willed to the Royal Society. Leeuwenhoek’s peculiar habits was this practice;
when he found a specimen particularly to his liking, he left it attached to the
microscope and made another instrument. Over the years he accumulated many of these.
He placed these in pairs in small lacquered boxes, 12 to 24 boxes in a case. One
such case he willed to the Royal Society.
Leeuwenhoek was the first man to discover and to describe protozoa and bacteria
(which he called ‘animalcules”). He used “a grain of sand”
(roughly a cube of about 1/30 of an inch) as his standard of comparison, and described
sizes of his “animalcules” by estimating that it would take 1,000, 100,000
of them to equal the bulk of “a grain of sand”. Some of his estimates
of identifiable species show a remarkable relation to modern micron measurements.
He described with no little wonder the tremendously rapid multiplication of his
“animalcules” when samples were allowed to remain standing for a few
days; and he was aware of the relative purity of fresh rain water or snow water.
Leeuwenhoek made drawings representative of various protozoa, bacilli, cocci, and
spirochetes. He studied animal parts, such as blood, bones, eyes, hair, and muscles;
he was the first to note striations in muscle fibers; and he is known, particularly,
for his study and descriptions of spermatozoa. In his world of microscopic biologic
forms, he saw: cellular division, birth, life and death of his “animalcules”;
parthenogenesis of aphids: and budding of hydra. He even tried to observe the explosion
of gunpowder under the microscope- an experiment that almost cost him his eyesight.
In one of his letters, after reporting on his observations on microscopic forms
both in wine vinegar and in scrapings from between his teeth, Leeuwenhoek revealed
a wry bit of sophisticated humor:
“I have had several gentlewomen in my house, who were keen on seeing the little
eels in vinegar; but some of ‘em were so disgusted at the spectacle, that
they vowed they’d ne’er use vinegar again. But what if one should tell
such people in future that there are more animals living in the scum on the teeth
in a man’s mouth, than there are men in a whole kingdom? Especially in those
who don’t ever clean their teeth?...”
Leeuwenhoek also reported, in 1686, and frequently demonstrated for visitors, the
capillary circulation of blood by placing a very small eel or fish in a glass tube
and focusing on the transparent tail. Malpihi had preceded him, in 1661, in this
observation, but it is doubtful that Leeuwenhoek knew of Malpighi’s work.
Leeuwenhoek also concluded that vessels leading away from the heart were arteries
and those toward the heart were veins, bearing out, by ocular observation, facts
about which Harvey could only conjecture.
As soon as his discoveries became famous, Leeuwenhoek was visited by all manner
of people who wanted to look through his lenses. The list of names of celebrities
who called on him is long and impressive: included were travelers, writers, physicians,
noted scientists, statesmen, kings, queens, an emperor of Germany, and Czar Peter
the Great of Russia. Leeuwenhoek naturally felt flattered, but frankly confessed
in one of his letters that he was bored by such interruptions and preferred to be
left in peace to carry on his work. Also, he showed such callers only certain of
his specimens, refusing to reveal others; and at no time would he disclose his methods
of lens-grinding, or sell one of his microscopes.
Naturally, publication of observations of such a multitude of previously unknown
things gave rise to arracks from unbelievers, from jealous contemporaries, and from
those irked by Leeuwenhoek’s lack of formal training. Of such criticisms,
Leeuwenhoek wrote: “I am well aware that these my writings will not be accepted
by some… they’re still saying… I’m conjurer, and that
I show people what don’t exist… I well known there are whole Universities
that don’t believe there are living creatures in the male seed: but such things
don’t worry me; I know I’m in the right.’
Though handicapped by failing eyesight and by other rigors of old age, Leeuwenhoek
continued his observations and his letters until the end of his life. He dictated
the last record within 36 hours of his death. Leeuwenhoek died peacefully on august
26, 1723, in his ninety-first year, and his body was buried in Old church in Delft.
Neither physician nor surgeon; actually, in formal terms not even a scientist, Leeuwenhoek
was recognized by his contemporaries as well as by modern students as one of the
most painstaking observers of all time, and the first to report on the great and
wonderful world of microbes. Though Leeuwenhoek drew no conclusions regarding the
relationship of his “animalcules” to causation of disease or to contagion,
other persons soon connected the “little animals” with earlier philosophical
speculations regarding the existence of living germs of diseases. Though theoretical
implications of Leeuwenhoek’s observations were recognized, no one made real
or practical use of the knowledge during the next 150 years. Yet Leeuwenhoek’s
work laid the foundation for Pasteur’s pioneering and for the almost explosive
growth of bacteriology and of protozoology in the latter half of the nineteenth
century. The revolution in medical thinking and in medical practice which these
developments brought about has resulted in prolonging lives of countless millions
of people throughout the world during the past 100 years.
THE PICTURE
Antony van Leeuwenhoek, draper of seventeenth-century Delft, Holland, in his spare
time retired to his “closet” to observe the wonders of the microscopic
world through tiny lenses he laboriously ground and mounted. He was first to report
having seen “animalcules”- protozoa and bacteria- and confirmed by direct
observation circulation of the blood. Though 200 years were to elapse before practical
application of his discoveries contributed to medicine, his work laid the foundation
for modern medicine’s tremendous century-long on-slaught against diseases
caused by bacteria and other microbiologic forms of life.
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