Chap. 3 LIVING MATTER AND CELLS 37 



cells as droplets or granules. Crystals, pigment, and droplets of water and 

 waste matter are common cell-inclusions. 



Shapes and Sizes of Cells. The shape of a cell depends upon the viscosity 

 of its protoplasm, the pressure from other cells, and upon its function (Fig. 



3.7). 



Most cells are microscopic, with dimensions of a few thousandths of a 

 millimeter (1 mm. = 345 ot an inch). Certain nerve cells of man and other 

 large mammals have processes that extend from the cell bodies in the nerve 



Cell wall 

 Cytoplasm 

 Nucleus 



Cells have thickness 



Cells are usually seen in slices 



B 



Columnar often with cilia 

 at one end 



Thin plates of 

 lining cells 



Cuboided 

 for covering 



/^^^ 



Packed m cords 



.'. .. ' . l . i . i . i . i _L '|l ' i ' i l ' ■ t^»i.d*«g^i^ 



"""'•"'••''"" 'flT'i'i ill" liti'i"''''"'"^ 



Elongated in the direction of the pull 



Fig. 3.7. Shapes of cells. In a multicellular organism most of the cells are pressed 

 together, often flattened, or six- or eight-sided. It has been recently maintained that 

 packed cells are actually 14-sided. This is apparent only under special conditions 

 and observation. A. Diagram of a cell cut in section as cells are commonly studied. 

 B. The shapes of these cells, muscle and others, are correlated with their special 

 functions and also affected by crowding. 



