The word cell is derived from the Latin word ‘cellula‘ which means “a little room”. An English scientist, Robert Hooke (1635-1703), in 1665 discovered and named the cells, while examining a thin slice of bottle cork under a primitive microscope made by him.
Hooke observed cork’s honey combed or porous structure
. Hooke found porous structure of cork to resemble with monasteries and called the units, cells. He pulished his work in a book “Micrographia” in 1665.
In 1674, Anton von Leeuwenhoek (1632-1723), a Dutchmicroscopist, made an improved microscope
and using this microscope he discovered the free living cells in pond water for the first time (1674). In 1678, he discovered sperm and identified the sperm cells of humans, dogs, frogs,fish and insects.
However Hooke had only seen the thickened walls of the cells and not the substance contained within these walls. In 1831, a Scottish botanist, Robert Brown (1773-1858) discovered and named the nucleus in plant cells. J.E. Purkinje (1787-1869), a Czech animal physiologist, in 1839 gave the term protoplasm for the living fluid substence present inside the cell. In 1866, Hackel established that the nucleus was responsible for storing and transmitting hereditary characters.
Cell Theory. In 1838, Jakob Matthias Schleiden (1804-1881), a German botanist,first proposed the idea that all plants consist of cells. Ayear later, in 1839 , Theoder Schwann (1810-1882), a German zoologist, independently asserted that all animals and plants are made up of cells. This joint finding forms the basic of the cell theory.
The cell theory was refined futher in 1855, when another German biologist, R. Virchow presented the idea that all cells arise from pre-existing cells (His actual aphorism was ‘Omnis cellulae a cellula‘). Thus, the cell theory comprises of the following postulates:
1. All organisms are composed of cells and cell products (e.g., secretions).
2. All metabolic reactions take place in cells. Thus, cells are structural and functional units of life.
3. All cells arise from pre-existing cells only. No cell can originate spontaneously or de novo (anew) but comes into being only by division of already existing cells.
4. Every organism starts its life as a single cell. Viruses are an exception to cell theory.
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