26 



THE ESSENTIALS OF HISTOLOGY 



elsewhere in the body) ; in the ventricles of the brain, and the central 

 canal of the spinal cord ; and in the convoluted tubules of the kidney. 

 Transitional epithelium is a stratified epithelium consisting of 

 only two or three layers of cells. It occurs in the urinary bladder, 

 the ureter, and the pelvis of the kidney. The superficial cells (fig. 

 26, a) are large and flattened ; they often have two nuclei. On their 



FIG. 26. EPITHELIAL CELLS FROM THE BLADDER OF THE RABIJIT. (Magnified 



500 diameters.) 



a, large flattened cell from the superficial layer, with two nuclei and with strongly marked 

 ridges and intervening depressions on its under surface ; &, pear-shaped cell of the second 

 layer adapted to a depression on one of the superficial cells. 



under surface they exhibit depressions, into which fit the larger ends 

 of pyriform cells, which form the next layer (fig. 26, b). Between 

 the tapered ends of the pyriform cells one or two layers of smaller 

 polyhedral cells are found. 



