38 THE VETERINARY SCIENCE. 



account of the space between the lung's and chest being' air tight 

 the lungs themselves enlarg"e and the air rushes in to fill up space. 

 The act of forcing- the air out is performed by these muscles 

 which relax while others contract in such a manner as to close the 

 chest cavity and makes it smaller, thus the lung's also become 

 smaller and forces the air out. The act of breathing is performed 

 in a horse in perfect health sixteen times a minute. 



CHAPTER IX. 



URINARY SYSTEM. 



THIS system consists ol the kidneys, ureters, bladder and 

 urethra. The action of these organs is to deal with the 

 urine or what is commonly called the water of the animal, 

 which is <^ watery fluid secreted by the kidneys. It varies in 

 color, according to the condition of the animal's blood. 



The Kidneys are two in number — one on the right side and 

 one on the left side, and are situated just below the small of the 

 back — the right one being the furthest ahead. In shape, they 

 are long and narrow, and resemble the liver in color. In cutting 

 one of these kidneys open, it is found to be full of glands and 

 tubes, which secrete the urine from the blood while it is passing 

 through the kidneys. These tubes pass to the centre of the 

 kidneys, where they empty the urine into what is called the pelvis 

 of the kidneys. The glands are largely supplied with blood vessels 

 and nerves. In examining the kidneys, one will generally find a 

 large quantity of fat, which help to hold them to their place. 

 The use of the kidneys are to secrete the urine from the blood, 

 which contains a large amount of what is known as ureaic acid,, 

 and if not taken out of the blood by these glands, acts as poison 

 to the system. 



The Ureters are the tubes which carry the urine down from 

 the pelvis of the kidney to the bladder. They are two in number — 

 one situated on the right side of the pelvic or hip cavity and the 

 other on the left side close to the walls — and they enter one on each 

 side at the upper part of the bladder. They are only about the 

 size of an ordinary straw. 



The Bladder is situated in the pelvic or hip cavity. When 

 it is full it sometimes stretches out into the abdominal or 

 belly cavity. It consists of a body and neck. The bod" 



