CIRCULATION 



77 



Fig. 50 B.— A white blood corpus- 

 cle showing ameboid movement. 

 (From Fitz.) 



in appearance and in work. Through a high-power lens 

 the red corpuscles appear as flattened discs of a pale yel- 

 lowish red. Their great number is responsible for the 

 deep red color of the blood. This color is due to a 

 substance they contain called hemoglobin which has a 

 remarkable affinity for oxygen. Oxygen passes from 

 the air in the lungs into solu- 

 tion in the blood, but the 

 blood holds so little in solu- 

 tion that the body w r ould die 

 for lack of oxygen were there 

 not some way of storing it. 

 Hemoglobin holds oxygen in 

 a loose chemical combination 

 and acts as a storehouse. By 

 means of it the blood keeps on hand a sufficient supply 

 of oxygen to maintain a steady flow into those cells which 

 are deficient. 



Relation between Oxygen and Hemoglobin. — Oxy- 

 gen never passes directly into the hemoglobin from the 

 air in the lungs. It goes into solution first. While there, 

 if it comes in contact with hemoglobin, a new substance 

 called oxyhemoglobin is formed. This substance is 

 extremely unstable. Oxygen and hemoglobin separate 

 as readily as they unite and the oxygen goes into solu- 

 tion, never directly to the tissues. .Combination and 

 separation take place at the same time in accordance 

 with the relative amount of oxygen in solution and in 

 combination with hemoglobin. If at any given place 

 there is an excess of oxygen in solution very rapid pass- 

 age will take place into the hemoglobin in that vicinity. 



