KIDNEYS. 



149 



The Uriniferous Tubules. The kidney is a compound, tubular gland 

 composed of microscopic tubules whose function it is to secrete from the 

 blood those waste products which collectively constitute the urine. If the 



FIG. 19. LONGITUDINAL SECTION THROUGH THE KIDNEY, THE PELVIS OF THE 



KIDNEY, AND A NUMBER OF RENAL CALYCES. (Tyson, after Henle.) 

 A. Branch of the renal artery. U. Ureter. C. Renal calyx, i. Cortex, i'. 

 Medullary rays. i". Labyrinth, or cortex proper. 2. Medulla. 2'. Papillary 

 portion of medulla, or medulla proper. 2". Border layer of the medulla. 3, 3. 

 Transverse section through the axes of the tubules of the border layer. 4. Fat of 

 the renal sinus. 5,5. Arterial branches. ""Transversely coursing medulla rays. 



apex of each pyramid be examined with a lens, it will present a number of 

 small orifices, which are the beginning of the uriniferous tubules. From 

 this point the tubules pass outward in a straight but somewhat divergent 

 manner toward the cortex, giving off at acute angles a number of branches 



