EPITHELIUM OF THE BLADDER. 



125 



In the bladder of Man the following layers are met with pro- 

 ceeding from within outwards : 



I. THE EPITHELIUM. This is arranged in many tiers, the 

 several layers presenting the greatest differences in the cha- 

 racters of the cells. 



Most internally are found one or two layers of cells, which, 

 though varying much in size and form, are usually spheroidal 

 and polyhedric, or, especially when large, are somewhat flattened. 

 Their borders and angles are often so prolonged that their 

 under surface presents a concavity into which a cell belonging 



Fig. 164. 



Fig. 164. Epithelium of the bladder, a, One of the cells of the 

 second row ; 6, a cell of the first row; c, exhibits the first, second, and 

 third layers of the epithelium in situ . 



to the next series is received. The contents are moderately 

 granular, with one or two nuclei and distinct nucleoli. These 

 correspond to the cells that are frequently found in urine that 

 has been passed. In some instances delicate perfectly hya- 

 line bodies may be seen, which throw out projections at one 

 or several points of their walls without the occurrence of any 

 shrivelling or other change, an appearance that is exhibited 

 also by other epithelial cells. 



The next layer of epithelial cells (fig. 164, a, c 2) is distin- 

 guished from the rest by the regularity of the arrangement of 



