Some Important People and Events

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In 1668, Francesco Redi showed that maggots came from adult flies. Maggots did not spontaneously generate from rotting meat.

Microbes were first discovered by an amateur Dutch scientist named Anton van Leeuwehoek in the 1670s.

In 1768, Lazzaro Spallanzani boiled broth and sealed it in a glass flask. No microbes grew within the sealed flask. In fact, he found that the broth within the flask would remain sterile forever. Proponents of spontaneous generation didn’t like his experiment because they believed that the boiling of the broth and the sealing of the flask had somehow altered the air so as to prevent spontaneous generation from occurring. See how Louis Pasteur solved the puzzle.

Latin word:

vacca = cow

In 1796, Dr. Edward Jenner used Vaccinia (cowpox) to vaccinate against smallpox. He observed that milkmaids often suffered from cowpox but rarely suffered from smallpox. It occurred to him that cowpox prevented milkmaids from catching smallpox. Smallpox virus, a stable DNA virus, is no longer found in the wild. However, it is reportedly held in a freezer at the CDC. It is reported that the former Soviet Union may have refined smallpox for biological warfare.

1847 - Ignaz Semmelweis proved that hand washing prevented the spread of childbirth fever. Prior to this discovery, many doctors were responsible for infecting many of their patients. Oops.


1865 - Joseph Lister proved that chemicals –specifically phenol (a.k.a., carbolic acid) - can be used to prevent infection. An antiseptic is a chemical that prevents infection.


1890 – Robert Koch created experimental steps for directly relating a specific microbe to a specific disease:



1. Germ must be found in all sick animals, but not in healthy animals. a

2. Germ must be grown in culture.

3. Cultured germ should make healthy animals sick. b

4. Germ must be found in sick animal.


a. Sometimes healthy animals are carriers. (cholera and typhoid)

b TB, cholera and HIV-infection don’t always result in sickness

Cloze Activity


In the late 1800s, Louis Pasteur and Robert Koch helped develop the science of bacteriology when they discovered a link between bacteria, fermentation and disease. Louis Pasteur was a French chemist and microbiologist who finally put the spontaneous generation issue to rest in 1862. He showed (with swan neck flasks) that microorganisms only came from other microorganisms and that a sterile broth would remain so -unless contaminated by life.

From 1877 to 1887, Pasteur employed these fundamentals of microbiology in the battle against infectious diseases. He went on to discover three bacteria responsible for human illnesses: staphylococcus, streptococcus and pneumococcus.

Louis Pasteur discovered the method for the attenuation of virulent microorganisms that is the basis of vaccination. He developed vaccines against chicken cholera, anthrax and swine erysipelas. After mastering his method of vaccination, he applied this concept to rabies. On July 6, 1885, Pasteur tested his pioneering rabies treatment on man for the first time: the young Joseph Meister was saved.


In 1918-1919, the influenza pandemic occurred. 20 million people died worldwide! Influenza is a mutation-prone RNA virus and it underwent an antigenic shift that year; it changed so much that human immune systems could not recognize the virus. Pigs, ducks, chickens are mixing vessels for the viruses.




In 1928, Alexander Fleming discovered penicillin by accident. Howard Walter Florey discovered Alexander Fleming's work on penicillin about 10 years later. He purified the active ingredients, tested the antibiotic on mice and saw that it worked. Antibiotics helped us win World War Two. He was awarded the Nobel Prize for physiology or medicine in 1945 for work on penicillin.


In 1955, Jonas Salk made the Polio vaccine. He successfully disabled the virus so that it could not infect humans. The virus still had good antigens. Poliomyelitis- (Jonas Salk, 1955)

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