CHANGES IN AIR IN THE LUNGS. 



129 



or similar ones, should be adopted. We might say " oxygen- 

 ated blood," and " de-oxygenated blood ; " but here, again, is 

 a chance for misunderstanding, for the blood still has con- 

 siderable oxygen when it enters the lungs (unless of an ani- 

 mal suffocated). We have just seen that in breathing we 



BRONCHIAL TUBE 



FROM PULMONARY ARTERY 



TO PULMONARY VEIN 



Fig. 48. Exchanges between the Air and the Blood In the Lungs. 



only take into the blood about one-fourth of the oxygen of 

 the air that passes through the lungs. In like manner the 

 blood, passing through the tissues, gives up to those tissues 



