CHAPTER II 

 PROTOPLASM AND THE CELL 



Universality of Protoplasm. — It is a curious fact 

 that though the surface of the earth is enormously di- 

 versified there is almost no square foot of its area that 

 is without life. It is almost as striking a fact that 

 throughout the enormous range of living things there is 

 present a single living substance, protoplasm, which is 

 fundamentally alike wherever found. Some organisms 

 consist entirely of protoplasm, some highly organized 

 beings consist only in small part of living protoplasm 

 but chiefly of the products formed by it. 



Protoplasm Always Organized into Cells. — It will 

 be seen in a subsequent paragraph that the physical struc- 

 ture of protoplasm is such that it could not exist un- 

 supported in large mass. From this it follows that any 

 large organism must have some method of dividing the 

 protoplasm into smaller portions. In fact it is found 

 to be true, that wherever the living substance increases 

 largely in mass it is organized into distinct, very small 

 parts called cells. The term cell signifies an independent 

 bit of protoplasm. 



The Discovery of Cells. — Although living organ- 

 isms have been known from the earliest times, it is only 

 within the last two hundred and fifty years that they 

 have been known to consist of cells. The reason for this 

 is that previous to that time there were no means of 

 observing so small an object. Ordinary cells are too 

 small to be seen with the naked eye or even with a small 

 lens. They vary greatly in size, but an average cell in 

 a growing root-tip, for instance, is about one ten- 

 ia 



