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PRINCIPLES OE VETERINARY SCIENCE 



Z. 



kidney of the horse is heart shaped, weighs about 23 ounces, and 

 is placed under the upper ends of the last two ribs and the trans- 

 verse process of the first lumbar vertebra (Fig. 45). It is in 

 contact with the liver in front and the pancreas below. The left 

 kidney is bean shaped, weighs about 22 ounces, and lies about 2 

 inches further back than its fellow. 



Each kidney has on the inner border a hilus or opening for the 

 ureter and renal artery, vein, and nerves. A tough, fibrous 



capsule, which can be easily stripped 

 off, covers each kidney. On sec- 

 tion, two distinct zones of kidney 

 substance are seen (Fig. 46). The 

 outer or cortical substance is 

 reddish-brown in color, and con- 

 tains many minute, dark, pinhead 

 points, which are blood-vessel tufts. 

 The inner or medullary substance 

 is lighter in color and appears 

 striated, due to the hundreds of 

 uriniferous tubules. The pelvis is 

 the central cavity or basin where 

 the urine is received from the col- 

 lecting tubules. The renal artery 

 is remarkable for its great size. 



The kidney is composed of num- 

 erous tubules closely associated 

 with blood-vessels (Fig. 47). Each 

 uriniferous tubule commences at a 

 closed, expanded end which sur- 

 rounds the glomerulus, or tuft of 

 capillary blood-vessels, the whole mechanism being known as 

 the malpighian corpuscle. The tubule projects into the kidney 

 substance in a convoluted manner, forms two loops, and finally 

 opens into a collecting tubule which conveys the urine to the 

 pelvis of the kidney. 



The ureters are thick-walled ducts of small caliber, which 

 connect the kidney with the bladder. Their course is along the 

 sublumbar muscles into the pelvic cavity. They have muscle- 

 fibers in their walls. The backward passage of the urine into 



Fig. 46. — Kidney of sheep; hori- 

 zontal section. 1, cortical sub- 

 stance; 2, medullary substance; 3, 

 renal crest; 4, renal pelvis; 5, 

 ureter. (From Leisering's Atlas, 

 reduced.) 



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