eguruchela

The Cell theory

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In 1838, German botanist (Mathias Schleiden), examined a large number of plants and observed that all plants are composed of different types of cells that form plant tissue.

Around the same time, British zoologist Theodor Schwann (1839) studied different types of animal cells and reported that cells have a thin outer layer known today as plasma membrane.

He also concluded on the basis of his studies on plant tissues that the presence of cell wall is a unique feature of plant cells.

On this basis, Schwann proposed the hypothesis that the bodies of animals and plants are composed of cells and the products of cells. Schleiden and Schwann together formulated the cell theory. However, this theory did not explain how the new cells were formed.

In 1855, Rudolf Virchow, explained for the first time that cells divide and new cells are formed from pre-existing cells (omnis cellula-a cellulae).

He modified the hypothesis of Schleiden and Schwann to finalize the cell theory. Cell theory as it is understood today:

(a) All living organisms are made up of cells and products of cells.

(b) All cells arise from pre-existing cells.