THE UROGENITAL SYSTEM 



99 



It is in contact with the liver in front and tlie pancrccas below. The 

 left kidney is bean shaped, and lies about 2 inches further back than 

 its fellow. Each kidney has on the inner border a Ihlus or opening 

 for the renal artery, veins, and nerves. Through this hilus the 

 ureter leaves. The average weight of the right kidney is about 

 23 ounces; that of the left, about 22 ounces. A tough, fibrous 

 capsule, which can V)e easily sti-ipjied off, covers each kidney. On 

 section, two distinct zones of kidney suljstance are seen (Fig. 30). 

 The outer or cortical substance is reddish-brown in color, and con- 

 tains many minute, tlark, pin-head points, which are the glomeruli 



;i'( nal ca s( 



Mi^duUnry suhstancc 



Jccc^^cni 



ardrn 



Renal arkry 



VrdcT 



Fig. 30.— Horizontal section of kidney. The \\'liitc areas are sections of 

 arteries. (Sisson, Anatomy of Domestic .Vninuits.) 



or blood-vessel tufts. The inner or medullary substance is 

 lighter in color and appears striated, due to the numberless urinif- 

 erous tubules which are found here. The pdvis is the central 

 cavity where the urine is received from the collecting tubules. 

 The renal artery is remarkable for its great size. The minute 

 structure of the kidney reveals on inspection a compound tubular 

 gland (Fig. 31). Each uriniferom tubule commences at a closed 

 exjianded end which surrounds the glomer}dm, or tuft of capillary 

 blood-vessels, the whole mechanism being known as the malpighian 

 body. The tubule projects into the medullary substance in a con- 



