SIMPLE E PIT HE LI A 



29 



cell it would he necessary to have at least se\eral sections at right 

 angles to and parallel with the long axis. In studying tissues and 

 organs, an attem])t should be made to \isuali/.e the third dimensional 

 aspect and consider the relationship of the cells with each other. 

 In the example just considered the cell was a regular, independent 

 unit, hut as a part of tissues all cells are modified by pressures of 

 adjoining cells and internal pressures, so that the connnon form is an 

 irregular })rism which in sections presents polygonal figures. In 



I 



Fig. 6. — Diagrams of the appearance of a variety of sections of a typical columnar 



epithelial cell. 



general, those cells which appear as squares in sections passing 

 through their central region at right angles to their base are spoken 

 of as cuboidal, but usually they are iso-prismatic in form. Likewise, 

 cells appearing as rectangles in sections passing at right angles to 

 their base are spoken of as columnar cells, but are long prismatic 

 structures when the third dimensional aspect is considered. The 

 squamous cells appear as fusiform structures in sections resulting 

 from cutting at right angles to their basal or attached surface. The 

 three types indicated show great variation as a result of irregularities 

 imposed by adjacent cells and the location of the tissue so that inter- 

 grading types are common. 



