THE URINARY ORGANS. 



163 



something to do with the prevention of a loss of albumin (Fig. 139). 

 In disease of the kidney, alterations in the glomerulus and, per- 

 haps, in other parts of the kidney permit albumin to pass into the 

 secretion. 



The epithelium lining the uriniferous tubules discharges its 

 secretion into the lumen of the tubules, whence it is carried by 

 the stream flowing from the Malpighian bodies. The epithelial 

 cells lining the convoluted tubules and the ascending branches of 

 Henle's tubes appear to be those most active in carrying on the 

 eliminative function of the kidney. 



2. The pelvis of the kidney and its calices are lined with trans- 

 itional epithelium. It consists of only three or four layers of 

 epithelial cells of different shapes. The most superficial layer is 

 composed of rather large flattened cells, having ridges upon their 

 lower surfaces, which fill the spaces between the tops of the next 

 layer. This is made up of pear-shaped or caudate cells, the hemi- 

 spherical tops of which fit into the cavities between the ridges on 

 the layer above, while their slender processes penetrate between 



FIG. 140. 



Epithelial cells from the pelvis of a human kidney. (Rieder.) 



the oval or round cells that make up the deepest layers of the 

 epithelial covering (Fig. 140). 



Beneath the epithelium is a coat of fibrous tissue, denser near the 

 epithelium and more areolar in its deeper portions. Here it is 



