THE BLOOD AND ITS FUNCTIONS 125 



oglobin is a proteid, but it differs from most proteids, in 

 that it contains in addition to carbon, hydrogen, oxygen, 

 nitrogen and sulfur, a little iron. 



While inside living corpuscles, haemo- 

 globin is in solution, but if a number of 

 corpuscles are treated with ether and the 

 ether evaporated, hemoglobin will be left 

 behind in the shape of definitely formed 

 crystals; Fig. 67. FIG. GT.-CRYSTALS 



It will be easier to comprehend the rela- OF HEMOGLOBIN 



,.'.., IT FROM RED BLOOD 



tion which these corpuscles bear to a person CORPUSCLES 

 if the facts are stated something as follows: 

 In the blood of a man weighing 150 pounds there are floating 

 about 25,000,000,000,000 red corpuscles. These contain about 

 one and one-half pounds of haemoglobin, and their surfaces 

 equal about 3,827 square yards or the area of a surface 225 feet 

 long by 150 feet wide. (Compare this with the area of your 

 school grounds.) The capillaries in the lungs are so small that 

 these corpuscles pass through them practically in single file. In 

 this way a great area is exposed for the absorption of oxygen. 

 Where does this great number of red corpuscles come from, 

 and what becomes of them? Do they live as long as the rest 

 of the body, or are they being constantly produced and de- 

 stroyed? Clearly, there must be some way in which they are 

 constantly produced, for a person may lose much blood from 

 a wound and recover completely in a few days. The answers 

 to these questions are rather unexpected; in a healthy person 

 blood corpuscles are constantly being produced in the red 

 marrow of the bones, and they are being as constantly destroyed 

 in the liver and perhaps in the spleen. Indeed, the bile from the 

 liver is, in part, the waste from broken down red corpuscles. 

 How long a red corpuscle lives we have no means of knowing; 

 but it starts in the bone marrow, does duty as an oxygen carrier 

 for a while, and finally ends its life in the liver or spleen. 



