TWELFTH LECTURE. 



THE URINARY SYSTEM. 



682. The urinary S3'stem consists of the Kidneys, Ureters, 

 Bladder, and Urethra, and by these organs the urine is extracted 

 from the blood, and expelled from the body. 



683. The Kidneys (Plate XV III., H., H. and Plate X XXVIII. , A. 

 1 . and 2.) are reddish brown, glandular bodies, situated in the under 

 part of the loins, — one on eac?i side of the back-bone. They are 

 supported and held in position by their vessels, aided by a quantity of 

 fat — the suet — in which the}' are embedded. The right one lies a 

 little farther forward than the left, being found beneath the two 

 last pairs of ribs. There is a marked difference between the shape 

 of the kidneys in the horse and cow. In the former, the right is 

 shaped like the heart of playing cards, the left being more like a 

 bean in shape. In the cow they are more elongated and distinctly 

 lobulated. 



684. Structure of the Kidney. — The organ is made up of tubes 

 (uriniferous tubes), blood vessels, nerves, and connective tissue ; the 

 whole being invested by a fibrous capsule. On making a horizontal 

 section of the kidney, it is found to consist of two distinct substances 

 separated by a well-defined line, which is dark in colour and known 

 as the bonndaiy layer. The external portion is known as the cortex of 

 the kidney ; the most internal part being the medulla. 



685. The Cortex. — On examination, a vast number of little red 

 spots called the Malpighian bodies are seen ; each of these consists of a 

 tuft of capillary blood-vessels (given off from the renal artery), enclosed 

 in a membranous capsule, known as the Capsule of Bowman. 



