Internal Respiration. 



105 



What the Blood gets from the Air. Oxygen from the air 

 in the vesicle passes through these layers into the plasma, 

 and most of it is quickly picked up by the colored corpus- 

 cles. The colored corpuscles are the carriers of oxygen. 



BRONCHIAL TUBE 

 FROM PULMONARY ARTERY ^_ -f TO PULMONARY VEIN 



Fig. 60. Exchanges between the Air and the Blood in the Lungs. 



Hemoglobin and Oxy-hemoglobin. The hemoglobin in 

 the colored corpuscles is eager to unite with- oxygen. 

 Hemoglobin is of a dark color, and gives the dark color 

 to the blood which enters the lungs. When oxygen unites 

 with the hemoglobin it forms oxy-hemoglobin, which is of a 

 bright red color. Hence the change in the color of the blood 



