Robert Hooke's microscope discoveries - Hooke's Macrographia Microscope history: Robert Hooke (1635 - 1703) The Englishman Robert Hooke (18th July 1635 - 3rd March 1703) was an architect, natural philosopher and brilliant scientist, best known for his law of elasticity (Hooke's law), his book Micrographia, published in 1665 and for first applying the word "cell" to describe the basic unit of life. It is also less well known that there is substantial evidence that Hooke developed the spring watch escapement, independently of and some fifteen years before Huygens, who is credited for this invention. Hooke also is recognised for his work on gravity, and his work as an architect and surveyor. Hooke's Micrographia Here, we focus on his pioneering work using the microscope to document observations of a variety of samples in his book Micrographia, published in September 1665.

Hooke began his famed career by initially studying at Wadham College, Oxford, where he worked closely under John Wilkins with other contemporaries, including Thomas Willis and Robert Boyle, for whom he built the vacuum pumps used in Boyle's gas law experiments. He also built some of the earliest telescopes, observing the rotations of Mars and Jupiter, and, based on his observations of fossils, was an early proponent of biological evolution. If that wasn't enough, he investigated the phenomenon of refraction, deducing the wave theory of light, and was the first to suggest that matter expands when heated and that air is made of small particles separated by relatively large distances, yet curiously Robert Hooke is somewhat overlooked in his contributions to science, perhaps as there were many people who wrote of Hooke as a difficult personality, being described as of "cynical temperament" and of "caustic tongue". There were also disputes with fellow scientists, including disputes with Isaac Newton over credit for work on gravitation and the planets. Though it must be remembered that Hooke lived at a time of immense scientific progress and discovery and none of the above diminish Hooke's inventiveness, his remarkable experimental facility, and his capacity for hard work.

In 1662 Hooke became Curator of Experiments of the Royal Society, meaning that he was responsible for demonstrating new experiments at the Society's weekly meetings. During this time, Hooke published the book Micrographia, an accurate and detailed record of his observations through his microscope (one of the best such microscopes of his time), illustrated with magnificent drawings. With it he observed organisms as diverse as insects, sponges, bryozoans, foraminifera, and bird feathers. Robert Hooke's microscope Perhaps his most famous observations were in his study of thin slices of cork, describing the pores, or "cells" he viewed. Hooke had discovered plant cells, or more precisely, Hooke had been viewing the cell walls in cork tissue. In fact, it was Hooke who coined the term "cells": the boxlike cells of cork reminded him of the cells of a monastery. Hooke also reported seeing similar structures in wood and in other plants. Hooke also famously described a fly's eye. The extract below from Micrographia demonstrates Hooke's perspective on how the microscope is utilised to enhance the senses...

"In the collection of most of which I made use of microscopes and some other glasses and instruments that improve the senses... only to promote the use of mechanical helps for the Senses, both in the surveying the already visible World, and for the discovery of many others hitherto unknown" - Micrographia, by Robert Hooke (1665) In addition to Hooke's observations, Micrographia is known for its spectacular copperplate engravings of the miniature world, particularly its fold-out plates of insects. The engraving of the louse in particular folds out to four times the size of the book. Although the book is best known for demonstrating the power of the microscope, Micrographia also describes distant planetary bodies, the wave theory of light, the organic origin of fossils, and various other philosophical and scientific interests of its author. Hooke also achieved fame in his day as Surveyor to the City of London and chief assistant of Christopher Wren. Hooke helped Wren rebuild London after the Great Fire in 1666, and also worked on designing many of London's landmarks, including the Royal Greenwich Observatory and the infamous Bethlem Royal Hospital (which became known as 'Bedlam').

Hooke's reputation was revived during the twentieth century and after a long period of relative obscurity he is now recognized as one of the most important scientists of his age. Different Types of Microscope: How to Select a Light Microscope How to select a light microscope How to Select a Light Microscope A look at the different types of microscopes and what they are used for The Englishman Robert Hooke (18th July 1635 - 3rd March 1703) was an architect, natural philosopher and brilliant scientist, best known for his law of elasticity (Hooke's law), his book Micrographia, published in 1665 and for first applying the word "cell" to describe the basic unit of life. It is also less well known that there is substantial evidence that Hooke developed the spring watch escapement, independently of and some fifteen years before Huygens, who is credited for this invention. Hooke also is recognised for his work on gravity, and his work as an architect and surveyor. There are many different types of microscope, but it is easier to split these into two main categories. Light microscopes and Non-light microscopes. What do we mean by light microscope?

A light microscope is a generic term for the type of microscope you would normally see on TV, being used by men in white coats in a scientific laboratory. Basically, a regular "microscope", with two eyepieces and a recognisable microscope shape. This is a light microscope, but could equally be called a compound microscope, or optical microscope. The descriptions are different, but they all refer to the same basic microscope. Each very different, but all are light microscopes However, there are many different sub-categories of light microscope, each with a specific purpose, since people have many different requirements when magnifying subjects. In order to know which type of microscope you require, there are some basic questions that need answering: What sample will you be looking at? What magnification do you require? Do you want to 'do' anything to the sample whilst being magnified? 1. What sample will you be looking at? Different samples have different physical properties and people want to look at almost anything under a microscope! For example, blood is very different to a diamond ring. If you are a microbiologist, your requirements for a microscope will be very different to a jewelry manufacturer. 2. What magnification do you require?

Red blood cells might typically be 6 - 8 µm in diameter, which is very small indeed! You will need a minimum magnification of around 400x to see red blood cells, but if you wish to view the cells in more detail, you will naturally need a greater magnification. Furthermore, blood will need to be prepared on a glass slide, so that you can view all the details you require. A diamond ring however is approximately 1.5cm in size, which you can see it with your eyes. If you are a jewelry maker, you will need to see all the intricate details of the ring, so 10x - 20x magnification would be fine. 3. Do you want to 'do' anything to the sample whilst being magnified? When setting a diamond in a ring, a jewelry maker will need to carefully place the precious stone in the setting of the ring. In order to do this, a 3-dimensional (stereo) view is required, since this provides depth perception, which aids hand-eye coordination, just in the same way that doing things with one eye closed is more difficult than using both eyes.

Although red blood cells are too small to 'do' anything with, you may want to look at different aspects of the cells. This could involve different preparation of the blood and/or different illumination techniques, such a darkfield, or phase contrast illumination (see illumination techniques ). So you can see that people have very different requirements when using light microscopes. 1635-1703 Robert Hooke was an English natural philosopher , architect and polymath who played an important role in the scientific revolution , through both experimental and theoretical work. His adult life comprised three distinct periods: as a brilliant scientific inquirer lacking money; achieving great wealth and standing through his reputation for hard work and scrupulous honesty following the great fire of 1666 ( but eventually becoming ill and party to jealous intellectual disputes. These issues may have contributed to his relative historical obscurity. Hooke is known for his law of elasticity ( Hooke's law ), his book, Micrographia , and for first applying the word " cell " to describe the basic unit of life.

Even now there is much less written about him than might be expected from the sheer industry of his life: he was at one time simultaneously the curator of experiments of the Royal Society and a member of its council, Gresham Professor of Geometry and a Surveyor to the City of London after the Great Fire of London, in which capacity he appears to have performed more than half of all the surveys after the fire. He was also an important architect of his time, though few of his buildings now survive and some of those are generally misattributed, and was instrumental in devising a set of planning controls for London whose influence remains today. Allan Chapman (a British historian of science) has characterized him as "England's Leonardo ". Hooke studied at Wadham College during the Protectorate where he became one of a tightly-knit group of ardent Royalists centred around John Wilkins . Here he was employed as an assistant to Thomas Willis and to Robert Boyle , for whom he built the vacuum pumps used in Boyle's gas law experiments. He built some of the earliest Gregorian telescopes , observed the rotations of Mars and Jupiter, and, based on his observations of fossils, was an early proponent of biological evolution .

He investigated the phenomenon of refraction , deducing the wave theory of light , and was the first to suggest that matter expands when heated and that air is made of small particles separated by relatively large distances. He performed pioneering work in the field of surveying and map-making and was involved in the work that led to the first modern plan-form map, though his plan for London on a grid system was rejected in favour of rebuilding along the existing routes. He also came near to deducing that gravity follows an inverse square law , and that such a relation governs the motions of the planets, an idea which was subsequently developed by Newton. Much of Hooke's scientific work was conducted in his capacity as curator of experiments of the Royal Society , a post he held from 1662, or as part of the household of Robert Boyle. Pioneers of Engineering | PAIEngineering Pioneers of Engineering Contact+1 225 292 9709 Pioneers of Engineering PAI Engineering owes deep gratitude to the founders of modern mathematical physics and their invaluable efforts to the benefit of mankind.

Our business is in particular based on the work of these individuals: Sir Isaac Newton Sir Isaac Newton FRS (4 January 1643 – 31 March 1727 [OS: 25 December 1642 - 20 March 1726]) was an English physicist, mathematician, astronomer, natural philosopher, alchemist, and theologian. His Philosophiæ Naturalis Principia Mathematica (Latin for “Mathematical Principles of Natural Philosophy”; usually called simply”Principia”), published in 1687, is probably the most important scientific book ever written, laying the groundwork for most of classical mechanics. Robert Hooke Robert Hooke FRS (18 July 1635 – 3 March 1703) was an English natural philosopher, architect and polymath who played an important role in the scientific revolution, through both experimental and theoretical work. Hooke is known for his law of elasticity (Hooke’s law), his book, Micrographia, and for first applying the word “cell” to describe the basic unit of life.

In mechanics, and physics, Hooke’s law of elasticity is an approximation that states that the extension of a spring is in direct proportion with the load applied to it. Many materials obey this law as long as the load does not exceed the material’s elastic limit. Materials for which Hooke’s law is a useful approximation are known as linear-elastic or “Hookean” materials. Hooke’s law in simple terms says that strain is directly proportional to stress. Carlo Alberto Castigliano Carlo Alberto Castigliano (9 November 1847 – 25 October 1884) was an Italian mathematician and physicist known for Castigliano’s method for determining displacements in a linear-elastic system based on the partial derivatives of strain energy. In the mathematics of structures, he is known for his two theorems: Castigliano’s first theorem, for forces in an elastic structure, and Castigliano’s second theorem, for displacements in a linearly elastic structure. Thomas Young Thomas Young (13 June 1773 – 10 May 1829) was an English polymath.

He is famous for having partly deciphered Egyptian hieroglyphs (specifically the Rosetta Stone) before Jean-François Champollion eventually expanded on his work. He was admired by, among others, Herschel and Einstein. Young made notable scientific contributions to the fields of vision, light, solid mechanics, energy, physiology, language, musical harmony and Egyptology. In solid mechanics, Young’s modulus, also known as the tensile modulus, is a measure of the stiffness of an isotropic elastic material. It is defined as the ratio of the uniaxial stress over the uniaxial strain in the range of stress in which Hooke’s Law holds.[1] It can be experimentally determined from the slope of a stress-strain curve created during tensile tests conducted on a sample of the material. It is also commonly, but incorrectly, called the elastic modulus or modulus of elasticity, because Young’s modulus is the most common elastic modulus used, but there are other elastic moduli measured, too, such as the bulk modulus and the shear modulus.

HOOKE'S LAW | 4 out of 5 dentists recommend this WordPress.com site HOOKE'S LAW 1 INTRODUCTION Today I am going to blog about an experiment I conducted at the University of Southhampton Physics Department on Hookes Law but before I share my findings with you guys, let us trace a brief Biography of the discoverer of this fundamemtal Material Properties which hold a great spectra in Engineering. 2 OUTLINE Henceforth this is the outline or legend for this blog. I will focus first on a borrowed paragraph of the Great man extracted from as 2.1 . I will then progress to 2.2 titled the H3W’s which I will expand on how atoms bond, why they fail under certain conditions, where their limit exist and when Hooke’s Law springs to action.Here I intend to take an all round prototypes of the material specimen deployed under the microscpe with an explicit notion to deduce a general conclusion.Section 2.3 will trace An Advanced Application of Hooke’s Law in Engineering, both benefits and draw backs. To conclude there will be a chance for comments and contribution.

2.1 BIOGRAPHY The Englishman Robert Hooke (18th July 1635 – 3rd March 1703) was an architect, natural philosopher and brilliant scientist, best known for his law of elasticity (Hooke’s law), his book Micrographic, published in 1665 and for first applying the word “cell” to describe the basic unit of life. It is also less well known that there is substantial evidence that Hooke developed the spring watch escapement, independently of and some fifteen years before Huygens, who is credited for this invention. Hooke also is recognised for his work on gravity, and his work as an architect and surveyor 2.2 THREE W’S AND H (HOW, WHEN, WHERE, WHY) Figure 1. 1 Cave man tools. As any lecturer or student of Engineering well knows, the vitality of the subject depends largely upon a continual synthesis of Theory with observation, and observation with Theory. Unfortunately this exercise is costly in terms of the time and the effort involved in finding sources. Now just spend a few minutes looking closely at the cave tools inserted above labelled as Figure 1.1.

These our ancestors with their primitive brains employed crude engineering to meet their basic survival needs to perfect their hunter gathering activities. Well some of you may ask what exactly has this got to do with my experiment? Bear with me and thank you for your kindred patience. All materials are built up from their individuals atoms. These properties of different materials arise from the ways their atoms are arranged on the molecular scale, and how the atoms and molecules pack together to form a microstructure. The cave men with no scientific observation selected materials which served their purposes with a blind knowledge and wisdom. For instance can you imagine the shock when striking two stones in a tropical temperature ignited; If only they patented their quack experiments, most probably they will be living today and well off than Mr. Bill Gates or a Russian Oligarch? It is obvious science has advanced immensely from its infancy , there continues to be great strides but today I hope to share with you the eloquence of Mr Robert Hooke and his Elasticity Theory. Is must be observed the Theory only holds for solids materials. To understand why a solid holds/ retains its shape, it’s because of interactions of atoms or molecules. A stretching force, or tension, applied to solids tends to pull the atoms apart.

This stretching is very small as a result of the huge cohesive intermolecular forces holding atoms close together. Similar in this way, compressing a solid pushes individual atoms closer together but then they will and must repel each other with a high magnitude force. A molecular arrangement of copper atom is incepted as figure1.2 as an insight into Atomic Structures at the molecular scale. Figure: 1.2 Intermolecular Bonding between Copper atoms Source: Okay I guess by now you may want to have a coffee break! I already have so I will crack on typing. I conducted a Hooke’s Law experiment for a cylindrical copper road, a steel rod and a glass rod. My data is tabulated in an excel table. I hope by now we are all convince with no contest as to how atoms co-exist at the molecular scale level. I so shall progress with why atomic bonding collapse when external forces of higher magnitude in relation to the valence band cohesive forces breaks such bonds. Hooke’s Law has a functional variety from springs to hydraulic tensile or compressive tests. Dependent on the test pieces and range of forces needed, this experiment from it simple foundation has advanced as its application resonates impeccably in most Engineering fields.

I have included two set-up of the apparatus required just for your viewing, Figures 1.2 and 1.3 respectively. Figure 1.3 Tensile and Compressive Apparatus Source: So when I applied a numerical sequence of forces from 1 to 9 Newton’s to my Steel and Aluminium solid rods materials , I find out that there was a distortion to an extend but this was still in the linear regions of the material. This is represented as the Y1 and Y2 in my excel table below. I realised the tensional force produced an Extension in each material i.e. the copper and steel. These extensions were directly proportional to the applied tensional force. This proportionality was first found by Robert Hooke (1635-1703) for materials shaped in a coil spring. Although such extensions do occur in wires or rods, they are very minimal. Table1.1 From my table X column is the force applied. The Y1=ax+b. However this is human syntax, the computer understands its own machine language but with abit of algebra, was able to compute the values of b to plot my first graph.

Excel utility showcased the gradient as 1.5583 and b =1.375. A Law stating that, in a linear system, the restoring force is proportional to the displacement of the body, acting in a direction as to restore equilibrium. Mathematically stated below using algebraic variables as placeholders. Where x = elongation of material [m] Graph1 Graph2 Y2 = (a+0.5) x + c. I employed basic simultaneous equation to solve for X and Y. X = 2.35 and y = 5.04. These are my intercept which is confirmed by the excel application. A word of caution to enter y2 equation follows this step. = 2*A3+0.2. This the language computer comprehends. A similar rule must be followed for Z3. The imperative outcome is that the graph is a straight line graph. I observed so far as I kept the Applied force reasonably small. My straight line graph demonstrates that the spring extends by equal amount for equal masses added. It thus support hereafter if my applied force is too great, the spring will not return to its original shape when I removed the force.

This is when the spring is said to have gone past its elastic limit and Hooke’s Law no longer applied. This is demonstrated in the graph below. Graph 3 A material such as copper, when stretched beyond its elastic limit it retains its shape. Such materials are said to be ductile or malleable. Can you think why copper has a lot of uses on an industrial scale? To the contrary, although Hooke’s law bear a true allegiance to most materials it does NOT hold for a particular group of materials such as rubber albeit rubber scientically is not classified as a solid. This is depicted in the graph below but with many scientific theories, there lest significantly is an expected margin of allowable tolerances. A quick example is Newton’s second law, “the force acting on a body is the product of it mass in kilograms and it acceleration due to gravity”. Yes this postulation is true but depending on which part on earth this law is applied, there exist a slight difference in the acceleration due to gravity g. For those of you rookies to this law, g, has an accepted mathematical value of between 9.81 to 10meters per Second Square.

Now there are some points on the graphs such as (7,13) and (9,15) which do not lie exactly on the straight. This is to be expected as the centre of mass/gravity was not accurately located but this is to be expected. Also the spring itself is aged; with it exposed to the environment in the lab, the temperature in the lab affect the material spring is composed of. However this happens at molecular scale so it affect on result is reduced. A material such as rubber, this does not follow Hooke’s law and remains elastic until it snaps. A material such as glass, this follows Hooke’s law until it snaps. Source: 2.3. ADVANCE APPLICATION OF HOOKE’S LAW I will make this as general as possible but fused with a lot of real life emphasis on Hooke’s Law. Those few lucky readers who have enjoyed a weekend getaway to the Swiss Alps, or South of France etc, if you happen to enjoy those magnificent summer or winter holidays in a Cable car, did you stop for a second to ponder why the high tensile steel ropes never snap after some many trips with temperature variation and forces? The Tacoma Narrows Bridge in Washington State was opened in 1940.

After four months it collapsed, not as a result of an earthquake, but because it was badly designed. It proved not strong enough for the loads it was designed to bear when exposed to violent winds. Closer to home the Humber Bridge use to be the longest suspension bridge anywhere in the World, spanning 1410 meters. The need to understand how materials behave when they subjected to forces is literally a life and death issue. Engineers know that they cannot rely on only theories when designing or building structures either small or massive. With lessons from the history books, now Engineers test design on models accurate to the minutest element before they begin to build. Then in progress safety checks conducted till project completion. 2.4 COMMENTS AND SUGESTIONS I am a foundation year student at University of Southampton. In writing this blog post assignment I have relied on some references to which I will give due accolade to their proprietors. I do however wish for constructive suggestions. To those of curious readers reach me through my e-mail: mamayendzi@yahoo.co.uk.

REFERENCE A LEVEL PHYSICS, R MUNCASTER PHYSICS, KEN DOBSON, DAVID GRACE, DAVID LOVETT IbnSina Avicenna 980 1037 An Arab philosopher and doctor His - BBF - 101 View Full Document  IbnSina Avicenna (980-1037) – An Arab philosopher and doctor. His most faous work was the canon of Medicine , A multi-volume textbookthat remained in used for over 500 years.  Anton van Leeuwenhoek (1632 - 1723) was a Dutch tradesman and scientist, best known for his work on the development and improvement of the microscope and also for his subsequent contribution towards the study of microbiology.  Robert Hooke (18th July 1635 - 3rd March 1703) was an architect, natural philosopher and brilliant scientist, best known for his law of elasticity (Hooke's law), his book Micrographia, published in 1665 and for Frst applying the word "cell" to describe the basic unit of life.

It is also less well known that there is substantial evidence that Hooke developed the spring watch escapement, independently of and some Ffteen years before Huygens, who is credited for this invention. Hooke also is recognised for his work on gravity, and his work as an architect and surveyor.  Carl Linnaeus (23 May 1707 – 10 January 1778), also known after his ennoblement as About this sound Carl von Linnéwas a Swedish botanist, physician, and zoologist, who laid the foundations for the modern biological naming scheme of binomial nomenclature. He is known as the father of modern taxonomy, and is also considered one of the fathers of modern ecology. Many of his writings were in Latin, and his name is rendered in Latin This preview has intentionally blurred sections. Sign up to view the full version. View Full Document as CarolusLinnæus (after 1761 Carolus a Linné).He received most of his higher education at Uppsala University, and began giving lectures in botany there in 1730.

He lived abroad between 1735 and 1738, where he studied and also published a Frst edition of his SystemaNaturae in the Netherlands.Linnaeus published Species Plantarum, the work which is now internationally accepted as the starting point of modern botanical nomenclature, in 1753. The Frst volume was issued on 24 May, the second volume followed on 16 August of the same yearThe book contained 1,200 pages and was published in two volumes; it described over 7,300 species.  Robert Brown (21 December 1773 – 10 June 1858) was a Scottish botanist and palaeobotanist who made important contributions to botany largely through his pioneering use of the microscope. His contributions include one of the earliest detailed descriptions of the cell nucleus and cytoplasmic streaming; the observation of Brownian motion; early work on plant pollination and fertilisation, including being the Frst to recognise the fundamental di±erence between gymnosperms and angiosperms; and some of the earliest studies in palynology.

He also made numerous contributions to plant taxonomy, including the erection of a number of plant families that are still accepted today; and numerous Australian plant genera and species, the fruit of his exploration of that continent with Matthew ²linders. This is the end of the preview. Sign up to access the rest of the document. TERM Polytechnic University of the Philippines BBF 101 - Fall 2015 Polytechnic University of the Philippines National Training Service Program Civil Wel Project proposal Discovery of Cells and the Developmwnt of Cell Theory Discovery of Cells and the Development of Cell Theory The study of cells started about 330 years ago. Before that time cells escaped notice because of their small size. With the invention of the microscope and its subsequent improvement, cells became visible and many new discoveries were made about them. Even today the study of cells reveals more detail, and its secrets, which are in fact the secrets of life itself, are revealed with ever increasing clarity. 1665: English Scientist and Microscopist Robert Hooke described a honeycomb-like network of cellulae (Latin for little storage rooms) in cork slice using his primitive compound microscope.

Robert Hooke used the term cells to describe units in plant tissue (thick cell walls could be observed). Of course he saw only cell walls because cork cells are dead and without protoplasm. He drew the cells he saw and also coined the word cell. The word cell is derived from the latin word cellula which means small compartment. Hooke published his findings in his famous work, Micrographia. Hooke, Robert (1635-1703), English scientist, best known for his sturdy of elasticity. Hooke also made original contributions to many other fields of science. Hooke was born on the Isle of Wight and educated at the University of Oxford. He served as assistant to the English physicist Robert Boyle and assisted him in the construction of the air pump. In 1662 Hooke was appointed curator of experiments of the Royal Society and served in this position until his death. He was elected a fellow of the Royal Society in 1663 and was appointed Gresham Professor of Geometry at Oxford in 1665.

After the Great Fire of London in 1666, he was appointed surveyor of London, and he designed many buildings, including Montague House and Dethlehem Hospital. Hooke anticipated some of the most important discoveries and inventions of his time but failed to carry many of them through to completion. He formulated the theory of planetary motion as a problem in mechanics, and grasped, but did not develop mathematically, the fundamental theory on which the English physicist Sir Isaac Newton formulated the law of gravitation. Hooke's most important contributions include the correct formulation of the theory of elasticity, which states that an elastic body stretches in proportion to the force that acts upon it; and analysis of the nature of combustion. He was the first to use the balance spring for the regulation of watches, and devised improvements in pendulum clocks. Hooke was also a poioneer in microscopic research and pulished his observations, which included the discovery of plant cells. Hooke's Microscope Hooke's drawing of Cork Cells 1670: Antonie van Leeuwenhoek (1632-1723) described cells in a drop of pond water using a microscope. A Dutch businessman and a contemporary of Hooke.

He also used microscopes and was a physicist. He made his own fine quality lens for use in monocular microscopes and was the first person to observe bacteria and protozoa. Some of his lenses could magnify objects 250X. Anton van Leeuwenhoek, born Oct. 24, 1632, was a Dutch biologist and microscopist. He became interested in science when, as a Dutch businessman, he began grinding lenses and building simple microscopes as a hobby. Each microscope consisted of a flat brass or copper plate in which a small, single glass lens was mounted. The lens was held up to the eye, and the object to be studied was placed on the head of a movable pin just on the other side of the lens. Leeuwenhoek made over 400 microscopes, many of which still exist. The most powerful of these instruments can magnify objects about 275 times. Although future microscopes were to contain more than one lens (compound microscopes), Leeuwenhock's single lens was ground to such perfection that he was able to make great advances and to draw attention to his field.

Leeuwenhoek was the first person to observe single-celled animals (protozoa) with a microscope. He described them in a letter to the Royal Society, which published his detailed pictures in 1683. Leeuwenhoek was also the first person, using a microscope, to observe clearly and to describe red blood cells in humans and other animals, as well as sperm cells. In addition, he studied the structure of plants, the compound eyes of insects, and the life cycles of fleas, aphids, and ants. Antony van Leeuwenhoek 1833: English Botanist Robert Brown discovered the nucleus in plant cells. 1838: Matthias Jakob Schleiden, a German botanist, concluded that all plant tissues are composed of cells and that an embryonic plant arose from a single cell. He declared that the cell is the basic building block of all plant matter. This statement of Schleiden was the first generalizations concerning cells. Born in Hamburg and educated in law at Heidelberg, Schleiden left law practice to study botany, which he then taught at the University of Jena from 1839 to 1862.

A man of disputatious nature he scorned the botanists of his day who limited themselves to merely naming and describing plants. Schlieden investigated plants microscopically and conceived that plants were made up of recongnizable units, or cells. Plant growth, he stated in 1837, came about through the production of new cells, which, he speculated, where prophagates from the nuclei of old cells. Although later discoveries proved him wrong about the role of the nucleus in mitosis, or cell division, his conception of the cell as the common structural unit of plants had the profound effect of shifting scientific attention to living processes as they happened on the cellular level-a change that initiated the field of embryology. A year after Schleiden published his cell theory on plants, his friend Schwann extended it to animals, thereby bringing botany and zoology together under one unifying theory. Matthias Schleiden 1839: Theodor Schwann, a German biologist, reached the same conclusion as Schleiden about animal tissue being composed of cells, ending speculations that plants and animals were fundamentally different in structure. Schwann described cellular strucures in animal cartilage (rigid extracellular matrix).

He pulled existing observations together into theory that stated: 1. Cells are organisms and all organisms consist of one or more cells. 2. The cell is the basic unit of structure for all organisms and that plants and animals consist of combinations of these organisms which are arranged in accordance with definite rules. In other words, the cell is the basic unit of life. This statement was the second generalization concerning cells and is the most important in the development of biology. It became known as the cell theory. Schwann, Theodor (1810-82), German physiologist, generally considered the founder of modern histology, the study of the structure of plant and animal tissues. Schwann was born in Neuss and educated at the universities of Bonn, Warzburg, and Berlin. He was (1838-48) professor of anatomy at the University of Leuven in Belgium; there after until his death he was associated with the University of Libge, also in Belgium, serving as professor of anatomy from 1848 to 1858, when he became professor of physiology.

Schwann achieved the physiochemical nature of life by applying the cell theory of the German botanist Matthias Jakob Schleiden to the evolution of animal life. He also demonstrated that the mature tissues of all animals are traceable to embryonic cells. While assisting the German physiologist Johannes Miller in the Anatomical Museum of Berlin, Schwann discovered pepsin, the digestive enzyme, in the stomach epithelium, or membrane tissues, of animals. He also conducted valuable research on the processes of fermentation, purefaction, and muscular and arterial contraction. His principal work is Microscopic Investigations on the Accordance in the Structure and Growth of Plants and Animals (1839-1847). Theodor Schwann 1840: Albrecht von Roelliker realized that sperm cells and egg cells are also cells.

1845 Carl Heinrich Braun Cells were first identified as the basic unit of life 1855: Taking Brown's original description of nuclei and observations by Karl N�geli on cell division, the German physiologist, physician, pathologist, and anthropologist Rudolf Virchow was able to add a third tenet to the cell theory: Omnis cellula e cellula, or all cells develop only from existing cells.Virchow, Rudolf (1821-1902), German pathologist, archaeologist, and anthropologist, the founder of cellularpathology. Virchow was born in Schivelbein, Pomerania (now Swidwin, Poland), and educated at theUniversity of Berlin. In 1843 he became prosector at the Charite Hospital in Berlin, and in 1847 a university lecturer. In 1849 he was invited to the medical school of Wurzburg as professor of pathological anatomy, having been dismissed from his Berlin posts because of revolutionary activities. In 1856 he returned to Berlin as professor and director of the university's pathological institute.

Virchow was the first to demonstrate that the cell theory applies to diseased tissue as well as to healthy tissue-that is, that diseased cells derive from the healthy cells of normal tissue. He did not, however, accept Louis Pasteur's germ theory of disease. He is best known for his text Cellular Pathology as Based on Histology (1850-1860). He engaged also in extensive research in the fields of archaeology and anthropology, producing numerous writings, among them Crania Ethnica Americana (1892). Other publications include discussions of topical political and social questions. Virchow was influential in German politics and from 1880 to 1893 served as a Liberal in the German Reichstag, where he opposed the policies of the German chancellor Prince Otto von Bismarck. He was instrumental in the establishment of the Pathological Institute and Museum in Berlin.

Question: Who is known for his law of elasticity, his book, "Micrographia", and for first applying the word "cell" to describe the basic unit of life?
Answer: Robert Hooke