162 



NORMA L HISTOLOG Y. 



bulk of the kidney, can be most easily understood if they are 

 traced back from their openings at the apex of the pyramid to their 



Fig. 138. 



W he 



Lobu/ e 



n al Pelvis 



Diagrammatic sketch of a section of the kidney: a, columnar epithelium covering the 

 external surface of the pyramid and continuous on the one hand with the columnar 

 epithelium lining the collecting tubules within the pyramid, and on the other hand with 

 the transitional epithelium lining the calices and renal pelvis. This transitional epi- 

 thelium is indicated at 6. It rests upon the fibrous tissue of the calices and pelvis, which 

 becomes continuous with the fibrous capsule of the kidney at the junction of the calices 

 with that organ. Outside of this capsule is the perinephric fat, indicated in the figure 

 between the calices. The vessels approach the kidney through this fat, entering its sub- 

 stance near the bases of the pyramids and forming the vascular arcades (e, arterial arcade). 

 From these arcades the interlobular vessels proceed, between the medullary rays and in 

 the labyrinth, toward the convex surface of the kidney, d, interlobular artery, giving 

 off branches, the afferent vessels, to the Malpighian bodies. The extensions of the cor- 

 tical substance between tbe pyramids, c, «xe known as the columns of Bertini. During 

 infancy the lobes of the kidney are marked by sulci upon the surface of the organ. With 

 the growth of the organ these lobes blend with each other, and the sulci between them 

 become indistinct ot are wholly obliterated. The columns of Btrtini are made up of the 

 blended lateral portions of the cortex of two contiguous lobes. 



origins in the Malpighian bodies. The different portions of the 

 tubules present somewhat different characters, and have received 

 special names. 



