60 Veterinary Elements. 



pure air and (2) fetch in pure air, and by carrying out 

 these two important things give (3) the means of warmth 

 to the animal. 



The processes of taking in food, using it and discharg- 

 ing the waste, have been described, there remains, how- 

 ever, the consideration of the respiratory (breathing) 

 organs — dual-purpose in character — because, as inti- 

 mated above, not only do they remove the waste poison- 

 ous gas (carbon di-oxide), but also are the means by 

 which that valuable gas — oxygen, without which no 

 animal life can exist, is brought into the system. 



The Organs of Respiration. The organs going to make 

 the respiratory system are the nostrils, nasal cavities, 

 pharynx, larynx, trachea, bronchi, bronchial tubes and 

 lungs. The nostrils are situated at the anterior extremity 

 of the nasal chambers, they are made up of cartilages, 

 which are dilated by muscles, and lined by mucous 

 membrane. At the upper part of the nostrils are two 

 blind pockets, called false nostrils; just inside the nostrils 

 are small openings, the point of exit of tears, brought 

 from the eyes by the lachrymal duct. A large nostril is 

 much desired, as the nostrils control the amount of air 

 taken in. The nasal chambers are two cavities separated 

 by a piece of cartilage (gristle), the septum nasi, in 

 each cavity are thin delicate curled bony plates, the tur- 

 binated bones, covered with mucous membrane, which is 

 thin and contains delicate blood vessels, consequently the 

 air is warmed as it passes over these bony plates before 

 being taken into the lungs. Pine nerves, constituting the 

 organs of smell, are also distributed in the nasal mucous 

 membrane. This mucous membrane is a pale delicate 



