-
1864 BCE
Louis Pasteur
He used the work of Needham and Spallanzani to recreate the experiment by designing several bottles with S-curved necks that were oriented downward. The air was able to reach the broth but any micro-organisms get caught up in the S-bend. He reasoned that the contamination came from life-forms in the air. Pasteur finally convinced the learned world that even if exposed to air, life did not arise from nonlife. (facts taken from speech given by Pasteur) -
Period: 1833 BCE to 1855 BCE
Cell Theory Scientists
1833- Robert Brown was the first to identify an important cell structure that is known as the Nucleus.
1838- Schleiden said that all living things are composed of one or more cells.
1839- Schwann stated that the cell is the basic unit of life.
1855- Virchow said that all new cells arise from existing cells. -
1745 BCE
Antoni van Leeuwenhoek
Anton van Leeuwenhoek used his knowledge of grinding lenses to achieve greater magnification and made improvements of which he utilized to make a microscope. This allowed detailed observations to be made of bacteria. Later on in the 18th century the development of achromatic lens improved the amount of detail that could be captured. -
1745 BCE
Lazzaro Spallanzani's experiment
He boiled two containers of gravy, assuming that the boiling would kill any microorganisms that were present. He then boiled broth and sealed the top of one and left the other open. After a few days had passed he saw the unsealed gravy was teeming with microorganisms, while the closed bottle was clean of microorganisms. -
1745 BCE
Needham's Rebuttal to Redi
He challenged Redi's findings by conducting an experiment in which he placed gravy into a bottle, applied heat to kill anything inside, then sealed it. Days later, he reported the presence of life in the broth and announced that life had been created from nonlife. In actuality, he did not heat it long enough to kill all the microbes. -
1668 BCE
Redi's Theory of Spontaneous Generation
Spontaneous generation, is the theory that life forms can be generated from inanimate objects, had been around since at least the time of Aristotle in about 350 B.C. Francesco Redi was able to disprove the theory that maggots could be spontaneously generated from meat using a controlled experiment. . -
1665 BCE
Hooke
Hooke's microscope had a 3-lens system. His microscope would have been the first "compound" microscope. The most famous observations were in his study of thin slices of cork, describing the pores, or "cells" he viewed. No achromatic lens were used. -
1595 BCE
Hans & Zacharias Janssen
The Janssen draw tube microscope was the first "compound" microscope-meaning that it utilizes more than one lens to magnify objects.
