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The evolution of the cell tehory
The theory of the cell and the most accepted model of the cell has changed many times since the discovery of cells. This is a timeline to demonstrate when, how, and why the cell model and theory has changed. -
Robert C. Hooke
King Charles II commisioned Sir Christopher to conduct a series of microscopial studies, but when he could not manage his time to conduct the study, the project was put in the hands of an upcoming scientist, Robert Hooke. While observing a cork with a microscope, Hooke observed many small pores (or cells) within it. While he did not know of the full extent of his discovery, he was impressed by the number of cells he counted within the cork (1,259,712,000). This was the first proof of cells. -
Antonie van Leeuwenhoek
Leeuwenhoek fillled a job position that allowed for great financial stability, which allowed him to focus more time on his hobby of grinding lenses and using them to look at smaller objects. He soon observed protozoa for the first time and bacteria a few years later, calling them "very little animacules" (the first seen living cells). In 1680, he made the first accurate model of a red blood cell and also disproved "spontaneous generation" by studying weevils of granaries (Sitophilus granarius). -
Henri Dutrochet
Dutrochet served as a military medical officer in Spain for several years before giving up that practice to devote his career to scientific research. When observing the similarities between plant and animal cells, he devoted his studeies to plant and animal physiology. He investigated respiration, light sensitivity. Dutrochet also stated "the cell is the fundamental element of organization", which is one of the fundamental tenets of modern cell theory. -
Felix Dujardin
Dujardin became chair of faculty and and a professor at two different Universities in France. He proposed a new group of one-celled organisms which he named protozoans through his studies of infusoria. Soon after that, while studying the openings in the calcoreous shell, he observed a formless life substance that exuded outward from the shell, calling it phytoplasm. Because of this work, Dujardin refuted the theory that microscopic organisms have the same organs as higher animals in 1835. -
Matthias Jacob Schleiden
Schlieden was a lawyer, but his hobby of botany quickly became his profession. Schleiden preferred to study plant structure under the microscope. He wrote “Contributions to Phytogenesis” where he stated that the different parts of the plant organism are composed of cells or derivatives of cells. This has become one of the most important statements in the history of the cell theory- confirming one of the tenets of the classical cell theory. He also studied the nucleus of the cell. -
Theodor Schwann
The same year Schwann became a professor of anatomy at University, he submitted his seminal work in which he extended the cell theory that had been developed the year before for plants by German botanist Matthias Jacob Schleiden to animals. In it he says that all animal tissues are made from cells and that all cells had to come from a single cell. This contradicted the previous theory that cells sporadically appeared. His theory also accepted the first two tenets of the classical cell theory. -
Rudolf Virchow
After graduating as a doctor, Virchow recorded and wrote a paper on one of the earliest known cases of leukemia. Through his study of many diseases, he concluded that the disease does not start in the organ or tissue, but within the individual cell itself. Using the theory that every cell comes from a preexistng cell, Virchow used this information in medical practices, advancing inflammation reearch. By proving this statement, he offered the 3rd and final piece of the classic cell theory.
