PSEUDO-STKATIFIED COLUMNAR EPITHELIUM 31 



only in the urinary system, this form of epithelium is always well 

 moistened. 



PSEUDO-STEATIFIED COLUMNAR EPITHELIUM. The su- 

 perficial cells only of this variety of epithelium are columnar in 

 shape, and except in one or two unimportant places are always 

 ciliated. The deeper extremities of these columnar cells taper to 

 a point, and extend all the way to the basement membrane. 

 Between the tapering ends of these cells small spindle-shaped and 

 spheroidal cells are closely packed. The several varieties of cells 

 thus appear to be superimposed, though all actually rest upon the 

 basement membrane. The distribution of this variety of the epi- 

 thelium is practically identical with that of ciliated cells. The 

 deeper extremities of the columnar cells are occasionally bifid or 

 even somewhat varicose in order the more closely to fit between the 

 spindle-shaped and spheroidal cells of the deeper portion. The 

 nucleus of these latter cells is usually situated a little below the 

 middle of the columnar cell, so that all the nuclei of the epithelial 

 membrane lie within its deeper half, thus giving to this portion 

 a more deeply chromatic appearance when observed in stained 

 sections under low magnification. The superficial half of the 

 epithelial layer contains only the cytoplasmic portion of the 

 columnar cells with their ciliated borders. 



