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100
Aristotle (384 - 322 B.C.)
A Greek philosopher who believed in the idea of spontaneous generation which dictated that life could arise from non-living objects and that there was no real boundary between living and non-living things. Non-living things could be animated by a “vital force” that was part of the air. He believed that sea slime or mud could spontaneously give rise to sea creatures and that decaying meat spontaneously gave rise to maggots. -
Period: 100 to
The Cell Theory
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Hans and Zacharias Janssen (1580-1638)
The father-son pair of Dutch lens grinders invented the first compound lens microscope, allowing small objects to be seen in much greater detail. -
Robert Hooke (1662)
English physicist Robert Hooke looked at a sliver of cork through a microscope lens and noticed some "pores" or "cells" in it. Robert Hooke believed the cells had served as containers for the "noble juices" or "fibrous threads" of the once-living cork tree. Hooke was the first person to use the word "cell" to identify microscopic structures when he was describing cork. He made the primitive microscope. -
Francesco Redi (1668)
Francesco Redi, an Italian physician, tried to determine if rotting meat turned into flies/maggots. In his series of experiments, he put pieces of meat in jars, leaving some open and others covered. He observed the jars and noticed that maggots came from the flies' eggs in the open jars and that these maggots metamorphosed into flies. Therefore, he concluded that meat cannot turn into flies and only flies could make more flies. This helped to disprove the theory of spontaneous generation. -
Anton van Leeuwenhoek (1673)
Anton van Leeuwenhoek (1632-1723) was a Dutch businessman used his own microscopes and was the first person to observe bacteria and protozoa in pond water. Leeuwenhoek's instruments were simply powerful magnifying glasses, not compound microscopes. Leeuwenhoek's skill at grinding lenses, together with his naturally superior eyesight and dexterity enabled him to see specimens at over 200 times magnification. -
Robert Brown (1830s)
Robert Brown, a Scottish botanist, observed a small and dark-stained sphere inside plant cells. He called this structure a nucleus. Brown's discovery was a key step in the development of the basic cell theory. -
Matthias Schleiden(1838)
As a botanist, he observed plants and plant cells. He observed that different parts of the plant organism were composed of cells. He inferred that all plants must be composed of cells. -
Theodor Schwann(1839)
As a physiologist, and a friend of Matthias Schleiden, Schwann had been studying animal tissues and cells. When Schleiden mentioned to Schwann that he had observed that plants were made of living cells, Schwann realised that his research on animal tissues had similar conclusions. Therefore, he combined the two ideas and formulated the statement that all living organisms were made of cells. -
Louis Pasteur
Pasteur became the first to show that living things come only from living things. He demonstrated that the microorganisms would grow in sterilized broth only if the broth was first exposed to air that contained their spores (reproductive cells). Pasteur's discoveries led to the development of the cell theory of the origin of living matter. The cell theory states that all life originates from preexisting living material. -
Rudolf (Rudolph) Virchow
Virchow’s greatest accomplishment was his observation that a whole organism does not get sick—only certain cells or groups of cells. In 1855, at the age of 34, he published his now famous aphorism “omnis cellula e cellula” (“every cell stems from another cell”). With this approach Virchow launched the field of cellular pathology. He stated that all diseases involve changes in normal cells, that is, all pathology ultimately is cellular pathology.
