162 NORMAL HISTOLOGY. 



The external surface of the kidney is covered with a capsule of 

 fibrous tissue, which on its deeper surface becomes continuous with 

 the interstitial tissue, so that its vascular supply communicates with 

 the capillaries in the superficial portions of the kidney. 



The fibrous capsule of the kidney becomes continuous at the 

 hilum of that organ with the fibrous coats of the calices and pelvis, 

 and, through these, with those of the ureter and bladder. 



The columnar epithelium lining the collecting tubes is continuous 

 with a layer of similar cells covering the papillae. 



The watery constituent of the urine is secreted in the Malpighian 

 body, where it passes from the blood through the capillary walls of 

 the glomerulus into the cavity of Bowman's capsule. Under nor- 

 mal conditions it is free from albumin, and, therefore, is unlike the 

 serum that passes through the walls of the capillaries in other parts 

 of the body. It has been thought that this difference was attrib- 



FIG. 139. 



KEr 



Capillary loop from the glomerulus of the frog. (Nussbaum.) Ez, endothelial wall of the 

 capillary bloodvessel; Ek, nucleus of one of the endothelial cells (only three such 

 nuclei are shown in the figure) ; KE, nucleus of one of the epithelial cells investing the 

 capillary. The boundaries of these cells are not reproduced in the figure. At the left 

 of the cut three epithelial cells have been partially reflected away from the capillary 

 wall. 



utable to the functional action of the endothelium in the glomerulus, 

 though morphologically it is similar to that throughout the body. 

 It is more probable that the epithelium covering the glomerulus has 



