12 



NATURE OF CELLS 



-n 



every vitally active plant and animal cell, this granular 

 liquid protoplasm is found. It is the essence of Ufe and is 



a wonderful substance. It 

 makes new flesh, blood, and 

 bone. In fact, protoplasm 

 does everything that is ac- 

 coniplishetl in an animal or 

 plant. 



In a living cell, the proto- 

 plasm is not of the same 

 structure throughout ; some 

 parts of it differing greatly 

 in structure and function 

 ~-sp. fi'om other parts. For ex- 

 ample, a small, well-defined 

 spot ma}' be seen, usually 

 along one side of the cell of 

 the melon hair, about mid- 

 wa}' of its length. This is 

 an organizeil structure of the 

 protoplasm known as the 

 mideiis. The remainder of 

 the protoplasm in the cell 

 is much thinner than the 

 nucleus, has a different func- 

 tion to perform, and is 

 known as cytoplasm. The 

 streams of cytoplasm seem 

 to nm to\\'ard the nucleus or 

 away from it. In other words they all seem to begin and 

 end there. lOven without other evidence this would show 

 that the nucleus must l)e very important. It is plain that 



Fjg. 3. - — A , liair of melon vine, show- 

 ing cells ; B, eell nivK-li enlarged ; sp, 

 streams of protoplasm; n, nucleus. 



