160 THE URINARY ORGANS. 



walls or processes of the cortical substance dipping down 

 between them, called the columnar Bertini; in these columns 

 the bloodvessels pass into the substance of the kidney. 



The adult human kidney is not normally divided into 

 lobes ; but in some mammals and in early human life the 

 kidney is lobed, each Malpighian pyramid with the adjacent 

 cortical substance forming a distinct lobe separated from other 

 lobes by clefts in the renal substance. 



The cortex of the kidney is a dark-red granular zone, much 

 narrower than the medullary region, and forming the periph- 

 ery, just underneath the capsule. It also sends processes 

 down between the Malpighian pyramids, the columnar Bertini 

 mentioned above. The substance of the cortex is divided 

 into the pyramids of Ferrein and the interpyramidal regions, 

 which alternate with one another. 



The pyramids of Ferrein, or medullary rays, or cortical 

 pyramids, are narrow bundles or sheaves of straight tubules 

 which radiate from the outer boundary of the Malpighian 

 pyramids through the cortex nearly to the periphery. These 

 cortical pyramids consist of straight portions of the uriuifer- 

 ous tubules, which are continuations of the radiating tubules 

 of the Malpighian pyramids, each of the latter giving off a 

 number of pyramids of Ferrein from its base. The tubules 

 in the centre are longer than those on the outside of each 

 pyramid of Ferrein, giving it the shape of a cone with a 

 narrow base. 



The intervals between the cortical pyramids are occupied 

 by the interpyramidal substance (or labyrinth) of the cortex. 

 This consists of the coiled and irregular portions of the 

 uriniferous tubules, twisting in all directions, studded and 

 intermingled with the numerous prominent round Malpighian 

 bodies, which give the cortex its granular character. 



The interpyramidal cortical regions comprise the active 

 secretory parts of the kidney; the pyramids of Ferrein and 

 Malpighi simply contain conducting tubules. 



The sustentacular connective tissue of the kidney consists 

 of the capsule, the intertubular or interstitial tissue, the peri- 

 vascular tissue, and the connective tissue lining the wall of 

 the renal sinus and continuous with the pelvis (ureter). 



The capsule is a firm fibrous membrane enveloping the 



