THE RESPIRATORY SYSTEM 97 



promptly rcmovocl. These facts emphasize the great importance 

 of proper stable ventilation and sanitation, and show that pure air 

 is an essential requirement for health. 



Oxygen is carried in the blood by the red blood-corpuscles. 

 The hemoglobin of the corpuscles is largely responsible for this 

 power. It has a marked affinity for oxygen, with which it easily 

 combines. 



The following table shows the approximate difference between 

 the gas content of human blood before and after it has circulated 

 through the tissues: 



O. CO2. N. 



100 c.c. arterial blood 20 c.c, 38 c.c. 1.5 c.o. 



100 c.c. venous blood 10 c.c. 48 c.c. 1.5 c.c. 



Difference 10 c.c. 10 c.c 0.0 c.c. 



These figures also signify that there is always a considerable 

 amount of carbon dioxid in arterial blood, and a corresponding 

 amount of oxygen in venous blood. Furthermore, they show that 

 the tissues do not remove all the oxygen, nor do the lungs remove all 

 the carbon dioxid from the blood circulating through them. 



There is some difference of opinion about the exact method of 

 absorption of oxygen by the fluids and cells of the body. For our 

 purposes the well-known chemical law of Dalton in relation to 

 changes in gases may be accepted as the explanation. 

 7 



