36 



ELEMENTARY TISSUES. 



stomach along the whole of the digestive canal to the anus, 

 and lines the principal gland-ducts which open upon the mucous 



FIG. 4. 



Cylindrical epithelium from intestinal villus of a rabbit; magnified 300 diameters 

 (from Kolliker). 



surface of this tract, sometimes throughout their whole extent 

 (a. Fig. 3), but in some cases only at the part nearest to the 

 orifice (b and c). It is also found in the gall-bladder and in 

 the greater portion of the urethra, and in some other parts, as 

 the duct of the parotid gland and of the testicle. It is com- 

 posed of oblong cells closely packed, and placed perpendicu- 

 larly to the surface they cover, their deeper or attached ex- 

 tremities being most commonly smaller than those which are 

 free. Each of such cells incloses, at nearly mid distance be- 

 tween its base and apex, a flat nucleus with nucleoli (B, Fig. 5) ; 



FIG. 5. 



Cylinders of the intestinal epithelium (after Henle) : B, from the jejunum ; c, cyl- 

 inders of the intestinal epithelium as seen when looking on their free extremities ; 

 D, ditto, as seen on a transverse section of a villus. 



the nuclei being arranged at such heights in contiguous cells 

 as not to interfere with each other by mutual pressure. 



4. In the fourth variety of epithelium cells, usually cylin- 

 drical, but occasionally of some other shape, are provided at 

 their free extremities with several fine pellucid pliant processes 

 or cilia (Figs. 6 and 7). This form of epithelium lines the 

 whole respiratory tract of mucous membrane and its prolonga- 



