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Life in a Time Before Microbiology
Illness and disease were thought to have a supernatural cause. Many people thought it was due to the wrath of God or evil spirits. The possibility of illness and disease being linked to unseen organisms was postulated, but not widely believed until the invention of the microscope and a series of experiments in the 17th century.
Galen of Pergamon 129 AD – 200 AD
Galen of Pergamon 129 AD – 200 AD was a pioneer in the fields of medicine, anatomy and philosophy. Galen' Galen created the Miasmatic Theory that postulates that disease is caused by "bad air" or "mal’aria", known as “miasmatic odors.” It was thought that these miasmatic odors arose from decaying organic matter and was the cause of diseases like cholera, chlamydia and the Bubonic Plague.
Although incorrect, the theory spurred the developed of better sanitation and hygiene practices. Aqueducts were built that brought in fresh water. Sewers were built that carried away waste and sewage. This practice protected the Romans from many waterborne diseases.
Although incorrect, the theory spurred the developed of better sanitation and hygiene practices. Aqueducts were built that brought in fresh water. Sewers were built that carried away waste and sewage. This practice protected the Romans from many waterborne diseases.
Hippocrates 460 - 370 BC
Hippocrates of Kos
(460 BC – 370 BC)
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Hippocrates was a Greek philosopher that lived 460–370 BC. He is considered the “father of Western medicine”. Hippocrates believed that illness and disease were caused by an imbalance among four vital "humors" within us. The idea was that if a person had either too much or too little of one of the humors, the result was illness or disease.
The 4 Vital Humors According to Hippocrates:
Hippocrates also authored many of the oldest known medical books and is said to have written the Hippocratic Oath that physicians still take today. The main theme of the Hippocratic Oath is to provide medical care without bias and to do no harm. |
Marcus Terentius Varr (116 BC - 27BC)
The Canon of Medicine by Abū Alī ibn Sīnā (Avicenna) proposed diseases like tuberculosis were contagious.
The Canon of Medicine (1020)
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 Agriculture by Marcus Terentius Varr
The first known record of the suggestion of micro-organisms, comes from 600 B.C. in a book on agriculture by Roman scholar, Marcus Terentius Varr. His book described micobes as "certain minute creatures that cannot be seen by the eyes, which float in the air and enter the body through the mouth and nose and there cause serious diseases. "
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Aristotle (384–322 BC)
and the
Theory of Spontaneous Generation
- Before Cell Theory...
- The Theory of Spontaneous Generation
Statue Depicting the Greek philosopher Aristotle (384–322 BC)
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The Greek philosopher Aristotle (384–322 BC) was among the scholars to publish the idea that living organisms could come from non-living things. This idea is known as the theory of spontaneous generation. Aristotle further postulated that life was able to arise from non-living matter if that non-living matter contained a supernatural substance he referred to as "pneuma" or "vital heat". The Greek word, pneuma means "breath" or "spirit".
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As odd as this theory may seem to us today, the idea of spontaneous generation was born from observations. For example, animals, worms or insects would seem to suddenly "appear" in an environment completely devoid of any visible evidence of life.
For example - Jan Baptista van Helmont, a scientist in the 1600's,, proposed that mice could arise from rags and wheat kernels left in an open container for 3 weeks.
- Fish would "appear" in a new puddle of water.
- Mice would "appear" in a pile of corn husks. or grain.
- Maggots would "appear" in rotting meat.
- Worms would "appear" from dead animals.
For example - Jan Baptista van Helmont, a scientist in the 1600's,, proposed that mice could arise from rags and wheat kernels left in an open container for 3 weeks.
Equivocal generation was a similar idea that postulated that living organisms arise from non-related living organisms.
For example,
These ideas were very different from the property of univocal generation which states that living organisms are created exclusively through the process of reproduction from genetically related parent(s), that we know to be true today.
For example,
- 1. Tapeworms could come into existence in an animal.
These ideas were very different from the property of univocal generation which states that living organisms are created exclusively through the process of reproduction from genetically related parent(s), that we know to be true today.
Germ Theory 1546
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In 1546, Girolamo Fracastoro came up with Germ Theory. Francastoro hypothesized that diseases may pass from one organisms to another through "transferable seed-like entities" that could spread diseases.
The germ theory of disease was not well-accepted by the population. The theory was even met with disdain. Scientists, physicians and the general public held fast to Galen's Miasma Theory.
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First Evidence Against Spontaneous Generation - 1668 by Francesco Redi
Italian physician Francesco Redi performed an experiment in 1668 that proved that maggots DO NOT spontaneously generate on rotting meat.
He Hypothesized that the appearance of maggots could be prevented by keeping flies away from meat. Meat that was exposed to air in which flies had access to the meat, produces maggots. Meat that were kept from direct contact with flies did not produce maggots.
He Hypothesized that the appearance of maggots could be prevented by keeping flies away from meat. Meat that was exposed to air in which flies had access to the meat, produces maggots. Meat that were kept from direct contact with flies did not produce maggots.
- First Evidence Against Spontaneous Generation - 1668
- The first evidence showing that the theory of spontaneous generation is incorrect, was presented by Italian physician Francesco Redi in 1668. Redi designed an experiment that disproved that maggots were able to spontaneously generate on rotting meat. His experiments also demonstrated that flies must have direct contact with the rotting meat in order for maggots to appear.
Francesco Redi (1626 - 1697)
Francesco Redi's 1668 Experiment
Redi Showed That Meat Kept Away From Flies Does Not Produce Maggots
Redi performed an experiment using six containers containing meat. Two were covered with gauze to prevent flies rom coming into direct contact with the meat, two were left open to the air allowing flies to have direct contact with the meat, and two were covered preventing flies from coming into direct contact with the meat. Redi's experiments showed that maggots could only appear when flies had direct contact with meat. Therefore, maggots were formed as offspring of flies and not from spontaneous generation by meat.
This observation existed, because the fly eggs that produced the maggots were too small to be detected with the naked eye. It was hard for even most scientists of the time to fathom the unseen microscopic world.
The Invention of the Microscope
Antique Microscope - Jansen's microscope consisted of three draw tubes with lenses inserted into the ends of the flanking tubes.
The first microscopes were simple and very limited in magnifying power. There is some debate surrounding who invented the first microscope, but there is evidence of early microscopes as early as the first century.
Zacharias Jansen and the first compound microscope
The first compound microscope was not invented until the 1590's. Zacharias and Hans Jansen were able to combine magnifying lenses together that resulted in an image that was 9 times larger than what could be seen with the naked eye.
Zacharias Jansen and the first compound microscope
The first compound microscope was not invented until the 1590's. Zacharias and Hans Jansen were able to combine magnifying lenses together that resulted in an image that was 9 times larger than what could be seen with the naked eye.
THE DISCOVERY OF CELLS AND CELL THEORY
All living beings are made up of cells. Some of them are made up of only one cell and others have many cells.
The adult human body is made up of about 37 trillion cells. That is 37,000,000,000,000 cells! WOW!!!
Robert Hooke (1635 - 1703)
- The Cell Theory began with Robert Hooke's discovery and observation of cells. As awesome as this discovery was, the true significance of this discovery was not fully realized until centuries later! It was only then that the structures Hooke coined as "cells" would be found to be the fundamental unit of life!
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Robert Hooke Observes Cells - 1660 Cells were first observed (and named "cells") by Robert Hooke in the 1660's. Hooke published his discoveries in 1665 in Micrographia,. Hooke named the small individual structures that made up plant and animal tissues "cell", because he thought they resembled the cells of a honeycomb.
It would still be hundred's of years until his discoveries and cell theory was widely accepted. |
Plant Cells View with a Compound Microscope
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Cells Were Named After the Cells of a Honeycomb (shown here) by Robert Hooke in 1665
Robert Hooke was the first person to view tissues under a microscopic. He identified the distinct structures that made up the tissue as "cells".
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Hooke published a book called Micrographia in 1665 in which he described and illustrated the microscopic view of a variety of samples and specimens.
In addition to his contributions to microbiology, Hooke made contributions to physics (Hooke's Law of Elasticity), astronomy, philosophy, and even architecture. Hooke's observations began with viewing sections of cork under the microscope. Hooke was observing plant cells which made up the cork. Hooke's book, Micrographia, included spectacular copperplate engravings of microscopic views of different organisms. Some of these, like the illustration of the louse, was a fold-out plate four times the size of the page. Interestingly, Micrographia also describes distant planetary bodies, the wave theory of light, evolution, etc.
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"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) |
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Robert Hooke identified the first cells by viewing a sample of cork.
He described cells as structures resembling a
Hooke decided to call these structures cells.. The word "cell" or Cell” is distinct from the others (in Latin, “cell” literally means “small room”). They likely appeared to Hooke to be filled with air because the cork cells were dead, with only the rigid cell walls providing the structure. |
Illustration of Microscopic View of Cork "Cells" by Robert Hooke
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Van Leeuwenhoek's Discovery of
Microorganisms in 1675
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Even though the existence of micro-organisms had been postulated throughout history, it was not until the invention of the microscope, that this micro-world was able to be seen!
 Antonie van Leeuwenhoek Improved upon the design of the microscope which enabled the discovery of mico-organisms
Early microscopes did not have much magnifying power, until 1675 when a Dutch cloth merchant named Antonie van Leeuwenhoek developed the first microscope lenses powerful enough to view microbes. The improvements resulted in a magnification power of up to 300X.
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In 1976, Leeuwenhoek was the first to observe single-celled organisms, he described as “animalcules” or “wee little beasties,” swimming in a drop.
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Cell Theory
The Cell Theory began with Robert Hooke's discovery and observation of cells. As awesome as this discovery was, the true significance of this discovery was not fully realized until centuries later! It was only then that the structures Hooke coined as "cells" would be found to be the fundamental unit of life!
- THE ORIGINS OF CELL THEORY
- Life comes in a huge variety of shapes, sizes, composition and physiology. Some of the largest organisms to ever roam the Earth, like the blue whale, exceed 150 tons, whereas the smallest organisms are only visible using microscopes. Our current understanding of "life" is centered on The Cell Theory which was developed over hundreds of years, due to the contributions of countless scientists and numerous inventions, experiments and observations. These discoveries were made possible due to the invention of high-powered microscopes in the 17th century.
All living beings are made up of cells. Some of them are made up of only one cell and others have many cells.
The adult human body is made up of about 37 trillion cells. That is 37,000,000,000,000 cells! WOW!!!
What is a cell?
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Rudolf Virchow - Archiv für Pathologische Anatomie und Physiologie (now known as “Virchow’s Archives”), 1847, first issue
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Matthias Schleiden (1804–1881)
Microscopic View of Plant Cells
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A botanist, Matthias Schleiden, took inventory of the microscopic view of hundreds of plant tissues.
Plant cells are very recognizable due to their pronounced cell walls, which gives them their characteristic brick-like shape. Interestingly, Schleiden believed the cell walls were due to some sort of crystallization process. We now know that the cell walls are created in the cell division process, not crystallization. |
Matthias Schleiden (1804–1881)
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Theodor Schwann (1810–1882) Theodore Schwann, a German physiologist, surveyed a multitude of animal tissue samples under the microscope and made several significant contributions to the Biological Sciences. Schwann and Schleiden realized the stark similarities between cells of plants and cells of animals.
Theodor Schwann and Matthias Jakob Schleiden were both instrumental in creating Cell Theory. In 1837, Schleiden stated that new plant cells were formed from old plant cells. Many of these observations were published in Schwann's book, Microscopical Researches into the Accordance in the Structure and Growth of Animals and Plants,. In it he declared, "All living things are composed of cells..." This statement is the heart of Cell Theory |
Theodor Schwann (1810–1882)
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Robert Remak (1815 – 1865)
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Robert Remak - 1852
Robert Remak performed experiments that presented convincing evidence that, indeed, new cells are formed from other cells through a process of cellular division. Remak's statements were met with disbelief by many of the prominent scientists of his time. The ideas of Cell Theory did not begin to be popularized until a publication by Rudolf Virchow, "Cellular Pathology". was published in 1857. Despite Remak's contribution, most texts attributed the founding of Cell Theory to Rudolf Virchow. In fact, some historians go so far as to declare that Virchow plagiarized Remak's ideas by stating that all cells come from pre-existing cells. |
Ignaz Philipp Semmelweis (1818 – 1865)
Ignaz Philipp Semmelweis (1818 – 1865)
Ignaz Philipp Semmelweis was instrumental in the development of aseptic techniques as a defense against the germs that were the cause of disease, according to Germ Theory, which had not yet gained popularity at the time. Semmelweis discovered that hand washing in obstetrical; clinics drastically reduced the incidence of "childhood fever", or puerperal fever.
Semmelweis was coined "the Savior of Mothers". Puerperal fever was common in the 1850's and was often fatal. Aseptic techniques he created involved disinfecting the hands with a chlorinated lime solution. He published a book of his findings in Etiology, Concept and Prophylaxis of Childbed Fever.
Semmelweis's discovery was tested and proved over and over again. However, the scientists of the day were reluctant to accept that hand washing reduced mortality rates, because the idea of Miasmatic Theory was prevalent and widely accepted within the medical and scientific communities. In fact, many medical practitioners refused to wash their hands and were insulted at the idea that their hands may be contaminated.
Semmelweis's ideas were finally popularized after his death, due to a series of experiments performed by Louis Pasteur confirmed the germ theory and Joseph Lister, who practiced and operated, using hygienic methods, with great success.
Semmelweis was coined "the Savior of Mothers". Puerperal fever was common in the 1850's and was often fatal. Aseptic techniques he created involved disinfecting the hands with a chlorinated lime solution. He published a book of his findings in Etiology, Concept and Prophylaxis of Childbed Fever.
Semmelweis's discovery was tested and proved over and over again. However, the scientists of the day were reluctant to accept that hand washing reduced mortality rates, because the idea of Miasmatic Theory was prevalent and widely accepted within the medical and scientific communities. In fact, many medical practitioners refused to wash their hands and were insulted at the idea that their hands may be contaminated.
Semmelweis's ideas were finally popularized after his death, due to a series of experiments performed by Louis Pasteur confirmed the germ theory and Joseph Lister, who practiced and operated, using hygienic methods, with great success.
Rudolf Virchow - 1857
Rudolf Ludwig Carl Virchow (1821 – 1902)
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The Cell Theory was then expand by Rudolf Virchow in 1857, to include the statement, "every cell arises from another cell".
Despite Remak's contribution, most texts attributed the founding of Cell Theory to Rudolf Virchow. In fact, some historians go so far as to declare that Virchow plagiarized Remak's ideas by stating that all cells come from pre-existing cells. |
Rudolf Virchow - Archiv für Pathologische Anatomie und Physiologie (now known as “Virchow’s Archives”), 1847, first issue
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“Golden Age of Microbiology”
1857 through 1914
Louis Pasteur (1822–1895)
Louis Pasteur's Swan-neck flask experiments
Louis Pasteur (1822–1895) experimented with growing bacteria in culture. Louis Pasteur proved that bacteria came from an outside source (like the air) and not from the growth media.
- Broth (growth media) was boiled before the experiments in order to kill any microbes.
- He incubated the broth protected from the outside air.
- He then repeated these experiments and allowed those samples to be exposed to the air.
- Nothing grew in the broths that were not exposed to air, therefore microbes did not spontaneously generate from the broth. Disproved the theory of Spontaneous Generation.
- Microbes did grow in the medium exposed to air, therefore microbes came from the air, as spores on dust, rather than spontaneously generated within the broth. These results supported Germ Theory.
Pasteurization 1864 Louis Pasteur invented a process that reduced the number of pathogens in certain food products, such as dairy products and alcoholic drinks like beer and wine. The process killed most of the bacteria that cause spoilage, thereby increasing food quality and protecting public health.
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Cream pasteurizing and cooling coils at Murgon Butter Factory, 1939
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Robert Koch 1876
Statue of Koch in Berlin
Robert Koch (1843 - 1910) is known as the founder of bacteriology. Robert Koch performed an experiment that provided evidence to the existence of bacteria. Specifically, Koch identifying the pathogens that cause tuberculosis, cholera and anthrax. Koch experimentally identified 4 generalized principles linking pathogens to disease. These principles were coined Koch's Postulates and still hold true today. Robert Koch was awarded the Nobel Prize in 1905 for his research on tuberculosis.
Koch's Postulates
- The organism must always be present, in every case of the disease.
- The organism must be isolated from a host containing the disease and grown in pure culture.
- Samples of the organism taken from pure culture must cause the same disease when inoculated into a healthy, susceptible animal in the laboratory.
- The organism must be isolated from the inoculated animal and must be identified as the same original organism first isolated from the originally diseased host.
John Snow 1848
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John Snow - the Father of Epidemiology In 1848, British physician John Snow conducted the first epidemiological study. He sought to discover the source of cholera outbreaks in London. Snow successfully traced the origins of the outbreaks to 2 water sources that were found to be contaminated with sewage. John Snow showed that disease is not only transmitted through the air, but can also through contaminated items, like water. Image Courtesy of By The original uploader was Rsabbatini at English Wikipedia - [1] Originally from en.wikipedia; description page is/was here., CC BY 4.0, https://commons.wikimedia.org/w/index.php?curid=403227 |
Joseph Lister (1827 - 1912)
 Joseph Lister in 1902
John Lister furthered the earlier work by Ignaz Semmelweis (1818–1865) that had developed the practice of sterile techniques and demonstrated the link between a non-sterile environment and disease. Sammelweis's ideas were met with disbelief by many members of the scientific and medical communities. Non-sterile environments were still commonplace, resulting in extraordinarily high (~ 50%) mortality rates among patients who had undergone various surgical procedures. Sammelweis demonstrated that the non-sterile environments that the patients endured during surgeries, lead to the development of these deadly post-operative infections. Sammelweis concluded that these infections due to unseen microbes that were able to travel through air or direct contact to the patients., causing illness and death. These infections were so common, they were termed "ward fever". The medical and scientific communities were more accepting of Sammelweis at this time, largely due to the overwhelming evidence produced by many scientists and physicians that proved the ideas of germ theory. |
Illustration of Lister Spraying Phenol Over Patient
The medical field adopted many of the aseptic techniques set forth by Lister. These methods of sterility and decontamination became the new standard for patient care. A great many of the aseptic techniques developed by Joseph Lister are still used in the medical field today.
FUN FACT! Listerine was developed in 1879 by Joseph Lawrence and was named after Joseph Lister, in honor of his contribution to antiseptic surgery. |
Conclusion
By the time of the 20th century, germs as the cause of disease was popularized and hygiene and sanitation as a prevention of disease became main-place.
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