340 *'- ' SPLANCHNOLOGY. 



Urinary System. , 



The organs of this system secrete tbe urine from the blood,* 

 and excrete or expel it from the body. These organs are 

 chiefly the Kidneys, Ureters, Bladder, and Urethra. The urine, 

 livhich is a watery fluid, is secreted by the kidneys, and carried 

 off by their ducts, the ureters, to a special reservoir, the bladder, 

 where it accumulates, and from which it is finally expelled 

 at intervals through the urethra. 



KIDNEYS. 



The kidneys are two compound tubular glands, situated on 

 the right and left of tlie vertebral column, in the sublumbar 



Fio. 120. 



Horizontal section of the right kidney, n, Fibrous capsule 

 detached ; b h b, Cortical layer ; n c, Medullary layer : d d d, 

 Cut ends of large blood-vessols : f. Pelvis of the kidney • 

 /, Ureter. 



region of the abdomen, in contact with the crura of the 

 diaphragm and psoe muscle?. They are supported by perito- 

 neum and cellular tissue, in which is deposited a quantity of fat ; 

 less perhaps in the horse than in other herbivorous animals. 

 The kidneys are also supported by their vessels as well as by the 

 pressure of the digestive organs ; the right one is in advance of 

 the left, lying just behind and baneath the last pair of ribs, 

 whereas the left one lies about two inches farther back. They 

 somewhat resemble in shape the heart on playing cards, the left 



r 



