The ancient Egyptians, from around 1500b.c., had already gained a rudimentary knowledge of human anatomy through their common practice of mummification. As the Egyptians removed key organs from the mummy-to-be, they learned certain facts about the organs and how they worked. The extent of Egyptian scientific discovery is to understand that the human body is made up of many components, all working together, which is a part of the second principle of the cell theory.
Aristotle was a greek philosopher around 384b.c. (timeline won't go to b.c.) Aristotle's contributions towards the cell theory include his many dissections, leading to his discoveries on the nature of life, and his rudimentary classifications of living things. Aristotle's classifications of different species show his knowledge that there are connections between every organism; this is shown through the first principle of the cell theory, that all living things are made of cells and thus similar.
1st Jan, 1000
By medieval times, Europeans had begun to develop an interest in biological attributes. Although much of the world was agriculture based, many people began to form questions about the scientific nature of life. Biology can trace many of its roots back to this era; therefore the cell theory can also trace its formation in this time.
1st Jan, 1543
He had a large effect on cell theory development through his studies of anatomy. He published the work "The Fabrica" , a study on human anatomy that is widely considered to be the world’s first scientific book on anatomy. His dissection of dead human bodies, cadavers, led to the most informative document of human anatomy of his time. His discoveries helped show how cells can work together in the human body to form complex organs, and therefore are the basic units of life.
Hans and Zacharias Janssen
These two men were the inventors of the first microscope. They constructed it around the 1590’s, yet the fact of who created it first is debateable. Either way their invention was further improved by other scientists, who used it to lead them to the first citing of a cell, thus leading into the cell theory.
He discovered that plants were comprised of similar boxes during an observation of fossil wood. He named those boxes cells, aiding to the creation of the cell theory by discovering the cell that it describes. He wrote a book describing his discoveries in 1665, called Micrographia.
Francesco Redi was the creator of the famous quote "Omne vivum ex ovo" ("All life comes from an egg"). This quote describes the third principle of the cell theory. His goal was to prove that life did not spontaneously occur, as it seemed to with maggots on meat. To disprove that idea Redi left out a jar of covered meat and a jar of uncovered meat, later finding maggots only on the uncovered meat. This finding convinced him that the maggots did not come from nowhere, but rather the outside world.
Anton van Leeuwenhoek
Anton van Leeuwenhoek’s interest in glass lenses as a young man led him to invent a lens that was could magnify an object by over 270 percent. He then used his powerful microscope to make major biological discoveries. He was considered the “father of microbiology’. Microscopes were essential in the discovery of the cell theory, for they allowed the study of the cell itself.
John Needham was an English microscopist who researched the spontaneous creation of microscopic organisms. He heated samples of broth, which he had previously checked for microorganisms, and then examined the broth again finding again microorganisms. This led him to the conclusion that spontaneous generation was possible. His results were wrong, however, due to the fact that he hadn't heated the broth hot enough to kill the organisms. His results were disproved by Spallanzani and others later.
Spallanzani disproved Needham's findings about spontaneous generation by using correct procedures that Needham had neglected. Spallanzani used airtight flasks and proper heating, giving him results that proved spontaneous generation to be false, the third principle of the cell theory.
Jean Baptiste Lamark
Lamark produced a flawed theory on heredity: ‘inheritance of acquired traits’ in 1801. Darwin and others recognized him as a good zoologist and his theory as a precursor to the theory of evolution. He discovered that the environment made organisms change their makeup, these changes were passed down through the generations. (Some organs got smaller, some bigger).
Oken created these new classifications for animals based on their evolutionary path: Dermatozoa- invertebrates. Glossozoa- fish with the first tongues. Rhinozoa- reptiles in which the nose opens into the mouth and us used for respiration. Otozoa- birds with the first externally open ears. Ophthalmozoa- mammals including all sensory organs. His classifications show an understanding of the similarities between organisms, which leads back to cells being the fundamental unit of life.
Robert Brown was a Scottish botanist who focused his studies on observation of plant cells through a microscope. His observations led him to discover the cell’s nucleus, and was the first scientist to describe the nucleus’ natural occurrence in living organisms’ cells. He gave the nucleus its name, and helped to develop the cell theory by attempting to understand the nucleus' importance in cellular activity.
In 1837 he developed the cell theory, with the help of other scientists, which summarized his findings and the findings of many other scientists over the centuries. He had previously discovered that cells do not spontaneously appearm, not for the first time yet solidifying past claims, thus leading to the formation of the third principle of the cell theory. His greatest contribution however was the organization of all of the scientific findings of cells into the cell theory.
Schleiden was one of the founders of the cell theory, obviously contributing to its creation by creating it. He worked with Schwann to create the final version of the cell theory. Schleiden worked with other scientists on the importance of the nucleus in cell division, as well as having detailed observations of plant development on a cellular level.
By using the cell theory, he created the modern concept of pathological processes. That concept describes the development and origin of pathogens, or diseases, in an organism. According to his process, diseases arise within an organism's individual cells, and then, based on the second principle of the cell theory that organisms are made of an array of connected cells, they travel to other cells.
Pasteur is famous for his invention of pasteurization, however he is also known for other accomplishments. Pasteur helped to disprove spontaneous generation, thus proving the third principle of the cell theory yet again. His discoveries led him to create the theory of biogenesis, which states that all life comes from preexisting life. Biogenesis sums up the third principle of the cell theory.