CHAPTER II 



PROTOPLASM AND THE CELL, AND ORGANISMS OF 



ONE CELL 



IF living things consisted solely of protoplasm, the larger 

 forms at least would appear little more than amorphous masses 

 of jelly. We have seen, however, that lifeless matter accompa- 

 nies living substance, and is laid down by this substance to form 

 supporting structures of one kind or other. Such larger forms 

 are made possible, furthermore, by the fact that the protoplasm 

 is divided up into innumerable units of structure termed cells, 

 each one of which has its own cell wall which is more or less 

 firmly attached to adjacent cells, thus giving mutual support 

 and solidarity to the whole. Lifeless matter deposited in 

 and around these cells adds further support and strength 

 (Fig. 12). 



Robert Hooke, an English botanist, in 1665, after studying 

 the structure of wood and higher plants, came to the conclusion 

 that cork and wood generally is made up of minute boxes which 

 he termed Cells. He believed that the walls were the essential 

 parts of the cell since the contents seemed invariably absent. 

 As microscopes improved, this conception of the finer structure 

 of living things became widely recognized, until in 1838-40 the 

 botanist Schleiden and the zoologist Schwann announced their 

 belief that all plants and all animals are composed of minute 

 units of structure to which, following Hooke, they gave the 

 name cells. But even they did not have the idea of cells that we 

 have today but regarded the walls as the vital parts. Proto- 

 plasm, as the fundamental living substance, was practically 

 unknown, although in 1835 a French naturalist Felix Dujardin 

 studied the structure of certain foraminifera or naked bits 

 of living matter without cell walls and published his conclusion 



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