The Cell Theory
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Rudolf Virchow
In 1855, the German doctor Rudolf Virchow proposed that all cells result from the division of previously existing cells, and this idea became a key piece of modern cell theory. It helped lead to the rejection of spontanious generation because it proved that cells can only come from other living cells.
Matthias Schleiden
In 1838, Schleiden discovered that all plants are made of cells. It helped lead to the rejection of Spontanious Generation because it proved that plants can't sprout directly from the Earth.
Theodor Schwann
Schwann proved the cellular origin and development of the most highly differentiated tissues including nails, feathers, and tooth enamel. Schwann made his contribution to the cell theory in the year of 1838. Theodor had asserted that cells might form out of cell products such as the extracellular material he called the "Cytoblastema"
Anton Van Leeuwenhoek
Leeuwenhoek contributed to the cell theory by teaching himself new methods for grinding and polishing tiny lenses of great curvature which gave magnifications up to 270x diameters. Leeuwenhoek contributed to the cell theory in the years 1674 through 1683. Anton help lead to the rejection of spontaneous generation by showing that bacteria will grow and animals don't come from abiotic things.
Robert Hooke
1665, the 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. He thought these cells existed only in plants, since he and his scientific contemporaries had observed the structures only in plant material.
Louis Pasteur
Today, Pasteur is often regarded as the Father of Germ Theory and Bacteriology (the study of bacteria), together with Robert Koch. Indeed, Pasteur showed that the growth of bacteria in nutrient broths is not due to spontaneous generation, but rather tobiogenesis (literally life from life). He further showed that fermentation is caused by the growth of micro-organisms. Finally, he showed that pasteurization(heating of liquids) sterilizes liquids and allows for long-term storage. The process was actually called 'pasteurization' as a way to honor Pasteur.