PHYSIOLOGY 



179 



puscles (erythrocytes) per cubic millimeter of volume in the male and 

 about 4,500,000 in the female. The average person, weighing 150 

 pounds, then, would possess approximately 20,000,000,000,000 (20 

 trillion) of them. Each erythrocyte is essentially a little capsule filled 

 with hemoglobin which is a compound peculiarly fitted to unite with 

 atmospheric oxygen. When united with oxygen it is known as oxy- 

 hemoglobin, which is readily reduced to give up the oxygen to the 

 cells when the blood reaches the tissues. The carbon dioxide given 

 off by the cells is collected principally in the plasma and returned 

 to the lungs. 



Average Characteristics of Human Blood Cells 



(Reproduced by permission from Textbook of Zoology by Storer, copyrighted, 

 1943, by McGraw-Hill Book Co., Inc.) 



