EPITHELIUM. 237 



lower portions of the nares, whence it passes into the frontal 

 sinuses, in the vagina and uterus, the lower two-thirds of 

 which it lines, as also the urethra. In the male subject 

 it passes over the glans penis, and then enters the urethra. 



The epithelium of the urinary apparatus should perhaps 

 be referred to the pavement epithelium : its cells however 

 vary very considerably in form : thus many of them de- 

 cidedly resemble the variety of epithelium under discussion ; 

 others, however, are clavate, the narrow or fixed extremity 

 being often produced into a long thread or filament ; and 

 again, others imperfectly represent the conoidal variety of 

 epithelium : these last, as well as the clavate cells, are met 

 with in the greatest quantity in the upper part of the 

 bladder, and in the ureters. 



CONOIDAL EPITHELIUM. 



Form and Size. The cells of this form of epithelium are 

 much more regular in size and shape than those of the tes- 

 selated or pavement kind : the term cylindrical usually applied 

 to them is, however, far from accurate, since they do not pos- 

 sess, even in a slight degree, the outward form of a cylinder : 

 the word conoidal, here used, serves to express much more 

 closely the real form of the cells of this variety of epithe- 

 lium, although it fails to give an exact idea of their shape : 

 thus the cells in question are not merely conical with flat 

 summits, but each cone is flattened at the sides, so that 

 when the bases of the cones are seen directly, they exhibit 

 the appearances of ordinary polygonal tesselated epithe- 

 lium ; the side view of the cells will at once make manifest 

 their distinctness. (See Plate XX. fig. 2.) 



Conoidal epithelial cells are usually disposed more or less 

 vertically to the surface upon which they rest, their narrow 

 extremities being turned downwards, and attached to that 

 surface, and the broader and free ends being directed 

 upwards. 



Structure. The cells of conoidal epithelium have pre- 

 cisely the same structure as those of the previously de- 



