THE URINARY ORGANS 317 



two, or three papillae. Each papillae has a number 

 of minute openings upon its apex for the excretory 

 ducts of the pyramids; the latter pour the urine into 

 the pelvis of the ureter. These orifices open into 

 tubules and are practically the external outlet of 

 the uriniferous tubules. They pass toward the base 

 of the pyramid, and within this region are known as 

 the tubes of Bellini. Continuing they enter the cortex, 

 where they become enlarged and twisted, and follow 

 an extremely tortuous course to turn backward into 

 the medullary portion for some space, and are called 

 in this position the ascending limb of the loop of Henle ; 

 they curve upon themselves again, and, while still 

 within the medullary portion, are known as the 

 descending limb of the loop of Henle ; reenter the cortex, 

 expand again, and becoming twisted (convoluted 

 tubule), end in an ovoid enlargement termed Bowman's 

 capsule, in which is a small collection of bloodvessels 

 the glomerulus, or Malpighian tuft. The capsule and 

 contained bloodvessels, the glomerulus, constitute 

 the small reddish bodies called renal or Malpighian 

 corpuscles, which are scattered throughout the cortex 

 of the kidney. 



The Cortex. This is reddish brown in appearance, 

 and lies just beneath the capsule of the organ. It 

 contains the Malpighian corpuscles. When examined 

 with a lens it has a light colored, ray-like appearance. 

 The lighter rays are termed the medullary rays, and 

 are found by the collection of uriniferous tubules (loops 

 of Henle) from the medullary portion. The darker 

 colored intervening substance is called the labyrinth, 

 from its complexity of structure, and is composed of 

 the Malpighian corpuscles and the various loops of the 

 tubules. 



The Uriniferous Tubules. Microscopic examination 

 of the kidney substance is the only method by which 

 the uriniferous tubules can be seen and understood. 



