22 EPITHELIAL TISSUES 



of endothelial membranes, squamous epithelial cells appear either 

 as mere lines or as spindle-shaped bodies whose bulging center 

 incloses the flattened nucleus. 



Fio. 19. SQUAMOUS EPITHELIUM OR ENDOTHELIUM (surface view). 

 From the mesentery of a rat. 'Silver nitrate and hematein. x 550. 



SIMPLE COLUMNAR EPITHELIUM. Simple columnar cells 

 occur as cylindrical bodies of varying length. Their deeper or 

 attached extremity often tapers nearly to a point, and is frequently 



bifid. A surface view of a mem- 

 brane consisting of columnar cells 

 shows the free extremity of each 

 cell to be of polygonal outline, the 

 cells collectively forming a beautiful 

 mosaic (Fig. 17). Each cell consists 

 of finely granular cytoplasm and con- 

 tains an oval nucleus, the long axis 

 of which corresponds with that of 

 its cell. The free extremity of these 

 cells has frequently a peculiarly fine 

 striated border, the cuticular mar- 

 gin ; it is distinguished from the body of the cell by a very deli- 

 cate membrane. When present, this peculiar striated border or 

 cuticle is characteristic of the columnar type of cell, and is specially 

 typical of those columnar cells which occur in the digestive tract. 



Fio. 20. COLUMNAR EPITHELIUM FROM 



THE PTLORIC REGION OF THE HUMAN 



STOMACH. (Profile view.) 

 Hematein and eosin. x 550. 



