122 



STUDIES IN PHYSIOLOGY 



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cal analysis shows the presence of 50 % of water and a 

 small amount of mineral matter. But the most important 

 ingredient is a proteid substance called hem-o-glo'bin (see 

 p. 18). This compound contains iron, and constitutes over 

 35 /o of red corpuscles. Hemoglobin gives the red color 

 to the blood and has the remarkable power of combining 

 with oxygen when that element is abundant, and of giving 

 it up wherever it is needed in the various parts of the 

 body. We may, therefore, compare the blood corpuscles to 



countless little boats, 

 floating in a stream of 

 plasma ; they take on 

 their cargo of oxygen 

 from the air in the 

 lungs and discharge 

 it to the cells of the 

 tissues. W r orn-out cor- 

 puscles are destroyed 

 in the liver and spleen, 



\u yjy an( j their place is 



P/ taken by new ones, 



which are produced, 

 as we shall learn, by 

 cells in the red mar- 

 row of bones. 



White Corpuscles. 

 We have seen that 

 white corpuscles re- 

 semble amoebas in their structure and activities. Let us now 

 study their functions in the human body. When one gets 

 a sliver of wood in one's finger and leaves it there for a time, 

 the finger becomes more or less swollen and sore, and white 

 pus or "matter" usually forms in the region of the wound. 

 All these effects are probably due to the presence of bacteria, 

 which were carried into the wound on the piece of wood. 

 Finding in the tissues favorable conditions for growth, these 



w*ss|5? 



FIG. 43. Human Blood Corpuscles. 



Magnified about 200 times. Photographed 

 through the microscope. The circular 

 disks are the red corpuscles. Near the 

 bottom of the photograph is a single 

 white corpuscle of larger size. 



