RESPIRATION 245 



RESPIRATION 



Respiration is a process whereby the lungs receive 

 the oxygen from the air we breathe; it is carried to 

 the tissues by the hemoglobin of the red cells, where it 

 is given off to the tissues; carbon dioxide is taken up 

 by the hemoglobin from the tissues and carried by the 

 red cells to the lungs, where it is given off in the expired 

 air. Respiration, therefore, is a function indispensable 

 to life and plays a most important part in the main- 

 tenance of body metabolism, by supplying oxygen to 

 the tissues, and removing carbon dioxide from the 

 tissues in the cheinic interchange taking place between 

 the air, the blood, and the tissues during the act of 

 respiration, and circulation of the blood. 



Rate of Respiration. The normal rate of respira- 

 ation varies at different ages as follows: At birth and 

 during the first year, 44 per minute; five years, 26 per 

 minute; fifteen to twenty years, 20 per minute; twenty 

 to twenty-five years, 18.7 per minute; thirty to fifty 

 years, 18 per minute. 



Respiration is divided into: inspiration, an active 

 process due to muscular activity, when air enters the 

 lungs, due to atmospheric pressure being greater 

 than the contained intrapulmonary; expiration, a quiet 

 or passive process, due to the recoil of the elastic 

 tissue of the lungs, the abdominal and thoracic walls; 

 when the intrathoracic pressure becomes greater than 

 the atmospheric air pressure it allows the contained 

 air to escape until the intrapulmonary pressure equals 

 the atmospheric air pressure, then inspiration occurs 

 again, and the respiratory cycle is repeated. 



The Volumes of Air Breathed. This is determined 

 by an apparatus known as Hutchinson's spirometer. 

 With this apparatus four volumes of air are deter- 

 mined. (1) The tidal volume or the amount of air 

 which flows into and ou^ of the lungs during an ordinary 



