CuaptTer III 
THE LIVING CELL 
THE CELL AS THE FUNDAMENTAL UNIT 
Robert Hooke, an Englishman, in 1665, first described and 
figured cells. He observed compartments regularly arranged in 
rows in thin sections of cork placed under a microscope and, 
likening these to the rooms of monasteries, named them cells. 
In 1831, Robert Brown, an English botanist, discovered the 
_nucleus which he found in a number of the plant cells. 
Matthias J. Schleiden, a German botanist, in 1838, showed 
the cell to be the unit of plant structure. The following year 
_ Theodor Schwann, a German zoologist, showed that the bodies of 
animals are also composed of cell units and announced the Cell 
Theory, based upon Schleiden’s earlier work and his own observa- 
tions. The bodies of all plants and animals are composed of one 
or more of these fundamental units of structure and function. 
Each cell consists of a unit mass of living matter to which Hugo 
Von Mohl gave the name of protoplasm in 1851. But protoplasm 
had been observed (though not so called) for the first time in 
the cells of some plants by Corti and Treviranus as early as 
1772 and in the cells of small animals by Dujardin in 1835. The 
latter described it as a jelly-like substance, ‘‘the primary animal 
substance,” and called it SAarcopE. The cell protoplasm may or 
“may not have a cell wall surrounding it. Most plant cells con- 
sist of a nucleated mass of protoplasm and a-cell wall surrounding 
it. The term Protop.ast is given to the mass of protoplasm 
found within the cavity of the cell. While most plant cells 
contain a nucleus and some contain a number of nuclei, the cells 
of the blue-green algze and the bacteria have been found to lack 
definitely organized structures of this kind but rather contain 
chromatin within their protoplasm in a more or less diffuse or 
loosely aggregated condition. 
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