"Of all the inventions
none there is Surpasses
noble Florentine’s Dioptrick Glasses
For what a better,
fitter guift Could bee
this World’s Aged Luciosity.
To help our Blindnesses
so as to devize
paire of new &Artificial eyes
By whose augmenting power wee now see
than all world Has ever doun Before.”
Henry Powers, 1664
the five senses, the most important is sight.It
aids in the process of gathering information about the environment that
we are part of.However, this visual
gathering is adequate only to a certain point. Beyond this point, the human
unaided eye fails to help us; the amount of detail that it can provide
is severely limited.In order to
overcome those limitations, humans started to develop instruments like
the magnifying glass, the spectacles, the telescope and the microscope.
earliest development of the microscope can be traced back to the ancient
world with the appearance of the magnifying glass, which was at that time
use as a “burning glass.”The conception
of the action of the magnifying glass with regards to the production of
a magnified image that could supplement the human eye first appeared in
the 13th century. It was at this time that the ancestor of the microscope
ancestor, the glass lens, first appeared.It
was discovered by Roger Bacon in 1268. As he tried to improve the
“burning glass,” he accidentally broke a crystal sphere and made several
observations through it. This led him to the following conclusion:
anyone examine letters or other minute objects through the medium of crystal
or glass or other transparent substance, if it be shaped like the lesser
segment of a sphere, with the convex side toward the eye, he will see the
letters far better and they will seem larger to him. For this reason such
an instrument is useful to all persons and to those with weak eyes for
they can see any letter, however small, if magnifier enough".(Bradbury,
The glass lens was initially
used to correct and compensate for defects in the human eye by improving
sight.Lens were incorporated into
spectacles or eyeglasses between 1268 and 1289, and they improved the vision
of people who had imperfect eyesight. A writer of a Florentine manuscript
dated 1299 in which he says:
find myself so pressed by age that I can neither read nor write without
glasses which they called spectacles, newly invented, for the great advantage
of the old men when their sight grows weak.” (Bradbury, 1968, 4)
took several hundred years before anyone assembled glass lenses in a way
that made distant objects appear close or small objects appear bigger.The
appearance of new scientific ideas in the seventeenth century - like experimental
philosophy and its beliefs that continuous experimentation and observation
as well as the improvement of the senses were needed for the better understanding
of nature- lead to the invention of instruments like the telescope and
telescope was invented in the 16th century by a Dutch optician
named Hans Lippershey.It was then
improved by Galileo Galile into a great astronomical instrument that allows
people to observe distant objects.With
this instrument, he observed moons orbiting Jupiter, which contradicted
the prevailing belief that all heavenly bodies revolved around the Earth.
This observation also confirms Copernicus' heliocentric theory. Galileo's
observations helped initiate the scientific revolution that has fundamentally
altered our world.
first microscope was developed in England during the final years of the
16th century.It is likely
that the microscope was a result of alterations made to the telescope.
It is believed that the microscope was discovered by accidentally inverting
a telescope, as indicated by the “account that one of the first microscopes
was six feet long and had a one inch barrel with a lens at either end”
earliest simple microscope was merely a tube with a plate for the object
at one end and a lens at the other end that gave a magnification less than
ten times the actual size.It had
just one lens, and although it had an unappealing look, it was capable
of extremely fine work like observing bacteria and single-celled animals.A
couple of years later in 1597, Zaccharias Jansseen and his son, Han Jansseen,
while experimenting with several lenses in a tube, discovered that a combination
of two lenses in a particular fashion. One lens was at the eyepiece
of the microscope (ocular), and the second lens was near the sample to
be studied (objective). This arrangement significantly enlarges the
sample under observation.It is believed
that their idea on the particular fashion of their lenses was based on
the reverse of a telescope, which explains why their instruments were two
feet long and extremely heavy.Nevertheless,
they evidently invented the forerunner of the compound microscope, which
was later modified in the 17th century by Robert Hooke.
the Jansen invention, word traveled rapidly throughout the known world.
More and more people took up the interest of observing things far smaller
than could be perceived with the naked eye.By
1625, optical workshops had been set up throughout Europe.
seventeenth century was a period of great interest in microscopy.
Some of the earliest discoveries and instrumentation were derived during
this period of scientific interest.During
this time, the word "microscope" was beginning to be accepted and regularly
used by the members of the first "Academia dei Lincei," a scientific society
that included Galileo. However,
the microscope wasn't just a scientific tool. Throughout this century and
also during Victorian times, microscopes were owned by the upper class
as recreational toys!
17th century, the first papers were published on microscopic findings.
The two most important papers were not published until 1660 and 1665, respectively,
when Marcello Malpighi proved William Harvey's blood circulation theories,
and Robert Hooke's wrote his "Micrographia."
Malpighi, Marcello (1628-94), Italian physiologist and one of the first
great microscopists, made discoveries in microscopic anatomy that upset
ancient medical beliefs and set the course for modern physiology.Even
today, he is considered the father of embryology and early histology.
Born in Crevalcore on March 10, 1628, Malpighi obtained a degree in medicine
and philosophy at the University of Bologna in 1653.As
professor of theoretical medicine at the University of Pisa, he began his
microscopic observations and became strongly critical of the assumptions
held in the fields of physiology and medicine.
In 1659 he returned to Bologna. In 1661, he made his most important
discovery, describing the network of pulmonary capillaries that connect
the small veins to the small arteries, thus completing the chain of circulation
postulated by the English physician William Harvey.Malpighi’s
microscopic observations provided crucial evidence for Harvey’s radical
ideas.Until that time, the ancient
belief had long prevailed that the blood was transformed into flesh on
the periphery of the body.
Among Malpighi's many other discoveries were his observations of the microscopic
components of the liver, brain, kidneys, spleen, bone, and the inner, or
what came to be known as the Malpighian, layer of the skin. He was the
first to discover red blood corpuscles and to show that they gave blood
its color. He also identified the taste buds and described the chick embryo,
the development of the silkworm, and the structure of plants.
Malpighi believed that living material was composed of minute glands that
separated or mixed the body fluids. Although he misunderstood the microscopic
functions of organs, he set the stage for cell theory and histology. His
discoveries of the hidden workings of organisms forced physicians of the
time to rethink firmly established assumptions. Although in his last years
he received such honors as being named personal physician to Pope Innocent
XII, his radical ideas cost him bitter and even violent opposition throughout
much of his life.
Hooke (1635-1703), an English scientist and mechanical genius, was born
on the Isle of Wight and educated at the University of Oxford.Hooke
was also a pioneer in microscopic research and published his observations,
which included the discovery of plant cells.His
Micrographia was an important milestone in proving the importance
of microscopy, and has granted him the title of English father of microscopy.
observed a thin slice of cork under the microscope and saw that it was
mostly air, which allowed it to float, be firm, and yet compress under
force.However, he also saw that
there were pieces of material making up sort of like a mesh-work of supporting
structures around the tiny pockets of air.Hooke
named these pockets of air "cells" after the small monastery rooms they
reminded him of.He had no idea that
those air pockets that he called “cells” were the remains of what is now
considered the primary structure of life. The name, cell, remains
until this day.
also developed and modified the Jansen compound microscope into a more
modern one, similar to the one we currently use.After
the compound microscope, the next major development was in lenses. Half
a century after the invention of compound microscope, both Robert Hooke
and Anthony van Leeuwenhoek realized that lenses with very short focal
lengths were the key to more magnification. This meant the use of double
convex or spherical lenses.
new double convex lenses improved the resolution, as well as the magnification,
of the compound microscope.It was
with this microscope that many discoveries in biology, especially in the
area of microbiology, were made.Among
the most important advances was the discovery of two infectious bacteria,
tubercle and cholera bacilli, by Robert Koch.
Robert Hooke published Micrographia in 1665. It is his most famous
work and is notable for the stunning illustrations, drawn by Hooke himself.Micrographia
is Hooke's most famous work, partly because of the brilliance of the illustrations,
and partly because of the extent to which his observations turned out to
be so far ahead of their time.
presents several accounts of Hooke’s observations through the use of the
microscope.He looked at all sorts
of things (snow, a needle, a razor, etc.) with a primitive compound microscope.But
his most significant observations were done on fleas and cork.He
observed the fleas under the microscope and was able to observe the tiny
hairs on the fleas’ bodies.On the
cork he saw pores. Upon examination of the pores, he decided to call
them “cells”; however, he did not know he had just discovered plant cells.
Antoni va Leeuwenhoek (1632-1723) was a Dutch maker of microscopes who
made pioneering discoveries concerning protozoa, red blood cells, capillary
systems, and the life cycles of insects.Born
in Delft, Holland, Leeuwenhoek received little or no scientific education.However,
his incredible discoveries in the field of microscopy granted him the recognition
as the father of microscopy.In recognition
of his discoveries, he was made a fellow of the Royal Society of England.
was a scientific amateur and as a hobby he devised single, tiny, double-convex
lenses mounted between brass plates and held close to the eye. Leeuwenhoek
taught himself how to grind and polish glass into a lens with a magnification
of 270X (a power that far exceeded that of early compound microscopes of
20-30X). He used this lens to make the world's first practical microscope.His
lens, unlike the lenses of the other microscope of the time, was a more
pure glass instead of the poor quality, greenish glass of the day.
confirmed and further developed the discovery by Italian anatomist Marcello
Malpighi regarding capillary systems, demonstrating how the red corpuscles
circulated through the capillaries of a rabbit's ear and the web of a frog's
foot. In 1674, he gave the first accurate description of red blood corpuscles.
In 1676, he then observed and described for the first time what he called
animalcules—known today as protozoa and bacteria—in pond water, rainwater,
in human saliva. In 1677, he described the spermatozoa of both insects
also opposed the prevalent theory of spontaneous generation, and through
the use of the microscope demonstrated that granary weevils, fleas, and
mussels were not created from wheat grains and sand but developed from
tiny eggs. He described the life cycle of ants, showing how the larvae
and pupae originate from eggs.Leeuwenhoek
also observed plant and muscle tissue, and described three types of bacteria:
bacilli, cocci, and spirilla. He kept the craft of making his lenses a
secret, however, so that not until the improvement of the compound microscope
in the 19th century were the next observations of bacteria made.
Leeuwenhoek is known to have made over 500 microscopes, yet fewer than
ten have survived to the present day.They
all had a basic design of a simply powerful magnifying glass; it was nothing
like the compound microscopes of the type use today.Compared
to modern microscopes, it was an extremely simple device, using only one
lens, mounted in a tiny hole in the brass plate that makes up the body
of the instrument.The specimen was
mounted on the sharp point that sticks up in front of the lens, and its
position and focus could be adjusted by turning the two screws.The
entire instrument was only 3-4 inches long and had to be held up close
to the eye.
the 18th and 19th centuries, the microscope went
through a time of several mechanical improvements that increased the stability
and facilitated a smooth focus and magnification.Among
other things developed during this time to improve the microscope was the
creation of microscope stages and slides in order to place and secure the
sample to be examined. Also, the development of objective lenses
improved and controlled the magnification and resolution of the sample.All
these mechanical improvements were added in conjunction with the new sampling
techniques that include the addition of water and chemicals to enhance
the view of the sample, as well as to stain the sample lead to the production
of a high quality clear image.The
ability of this new microscope to create such images caught the attention
of the scientific community and society in general. The microscope
became very popular once again, but this time it underwent a high-volume,
low-cost, mass production.
microscopes were still popular in the early 1900’s.
There was not much change in the fundamental basics of the microscopes
during this time, however there was a standardization of the parts as a
result of the high demands of supplies during the World War I.Among
the first standardizations, we find that most microscopes were made out
of cast-iron with a blackened finish and the eyepiece had been standardized
into a short tube of 23mm diameter.There
were many varieties of microscope manufactured during the 1900’s, but most
of them had the same general parts as seen in the picture to the left.
the 20th century new developments and improvements have rendered
the discoveries of the 19th century to be very basic.The
new microscopes are not only able to use light as a way of reflecting the
image of the sample, but they are more versatile and capable of using electrons
of high resolution power to examine a sample and reproduce its image.The
versatility of the microscopes allows one to observe a sample in a 3-dimensional
fashion rather than on a flat pain like the conventional microscopes.Also,
the magnification power of these new microscopes is incredible; they can
easily reach the 200,000x, or 10,000 times more than the earliest microscopes.
types of microscopes
are many types of microscopes, among the most important and recognizable
we can find:
microscope- uses two lenses, an objective lens and an ocular lens,
mounted at opposite ends of a closed tube, to provide greater magnification
than is possible with a single lens.The
objective lens is composed of several lens elements that form an
enlarged real image of the object being examined.It
has a firm stand with a flat stage to hold the material examined and some
means for moving the microscope tube toward and away from the specimen
to bring it into focus.
Microscope- uses electrons to "illuminate" an object. Electrons have
a much smaller wavelength than light, so they can resolve much smaller
structures.It has an electron gun
that emits electrons in a vacuum, which then strike the specimen and records
its image to display it in a monitor rather than through an objective lens.There
are two types of electron microscopes: the transmission electron microscope
(TEM), and the scanning electron microscope (SEM).Both
of them work under the same basic principle, with the exception that a
SEM scans the surface of a thinly sliced sample bit by bit and a TEM looks
at a relatively large area of the sample all at once. Scanning electron
microscopes can magnify objects 100,000 times or more.
probe microscope- uses a probe to scan the surface of a sample and
provides a three-dimensional image of atoms or molecules on the surface
of the object. The probe is an extremely sharp metal point that can be
as narrow as a single atom at the tip.It
provides detailed images of substances that can conduct electricity.In
addition, it has a sensing mechanism that records the up-and-down movements
of the probe and feeds the data into a computer, which creates a three-dimensional
image of the surface of the sample.
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