CELL BIOLOOY-INTRODUCTION (brief history of cytology)

 

Cell biology (Gr., kytos-hollow vessel or cell, logos-to discourse) is a biological science which deals with the study of cells. The cell itself can be regarded as the vital unit of organisms.

'Aristotle' and 'Paracelsus' concluded that "all animals and plants, how­ever, complicated are constituted by few elements which are repeated in each one of them."

The beginning of cell biology dates back to the 15th century, when 'Da Vinci in 1485 has stressed upon the use of lenses in viewing small objects. In 1658, 'Jan Swammerdam' gave the first description of the cell in his account of the red blood cells of the frog. The cytology came in its actual existence with the discovery of cell in 1665, by "Robert Hooke", while examining a thin slice of cork under his crude compound microscope, Hooke observed its honey-combed structure. He gave them the name "cells" (cellulae -little room).

Malphighi' studied a variety of animal tissues microscopically and there­fore, he is generally considered as the father of 'microscopic anatomy '.

'A.V.Leeuwen hoek (1632-1723) discovered the animalcules, infusoria (Protozoa), bacteria, etc., and made microscopical observations on protozoa, ants, aphids, spermatozoa, red blood cells etc.

The cell theory was proposed by two German biologists'M.J.Schleiden' (1804-1881), and Theodor Schwann' (1810-1882) independently in 1838 and 1839, respectively. The cell theory holds that the animals and plants have same pattern of organization and construction. The bodies of both animals and plants are composed of cells and that each cell can act independently. In words of 'Schwann' and 'Schleiden' cell is "functional biological unit'.'

"Rudolf Virchow" in 1885 stated, "where a cell exists there must have been a pre-existing cell, just as the animal arises only from an animal and the plants only from a plant".

"Purkinje" in 1840 coined the term protoplasm. The protoplasm was first of all observed by "Corti" (1772) and the French Zoologist 'Dujardin' (1835) called it sarcode.

"Huxley" in 1868 referred to protoplasm as the "physical basis of life".

The protoplasm theory states that all living matter of animals and plants is protoplasm. The part of the protoplasm which occurs between the plasma membrane and nucleus is named as cytoplasm.

20th century brought many modern micro techniques. New histo chemical and cyto chemical methods have been developed to detect various molecular components of the cell. Different biochemical events of the cell could be known by autoradiography. Methods of tissue culturing have made possible the study of living cells.

 

Year	Names of contributor	Cytological contribution
1824	R.J.H. Dutrochet	Showed that all animals and plants composed of cells.
1826	Turpin	Reported the occurrence of cell division.
1831	R. Brown	Described the nucleus
1835	Felix Dujardin	Described protoplasm as ("Sarcode")
1838	M.J.Schleiden	Proposed "Cell theory"
1839	T.Schwann	Applied "Cell theory" to animals.
1840	J.E. Purkinje	Named the cell contents as Protoplasm.
1855	R.Virchow	Stated that all cells arise from pre-existing cell.
1857	Kollieker	Discovered mitochondrian
1863	Waldeyer	Chromosomes of cell
1871	F. Miescher	discovered nucleo-protein and nucleic acid.
1882	Strasburger	described mitosis in plant cells
1887	E.Van Benden	discovered centrioles.
1888	T.Boweri	described the centrioles.
1888	Waldeyer	Introduced the term chromosome.
1902	W.S.Sutton	Proposed "the chromosome theory" heredity.
1905	J.B.Farmer along with J.E.Moore.	Coined the term meiosis
1943	A.Claude	Isolated cell components like ribosomes, mitochondria and nuclei
1952	C. Du Duve	Identified hysosomes.
1953	J.D.Watson and F.H.C. Crick	Proposed the double helixmodel for the DNA molecule.
1959	S.Ochoa	Synthesis of polyribonuclotide in vitro.
1959	A.Kornberg	Synthesis of polydeoxiri-
1968	M.W.Nirenberg and H.G.Khorana.	Triplet genetic code.
1968	R.H.HoIley	discovery of base sequence of RNA