REPAIR OF INJURIES 



399 



703. Injuries due to bacteria. If bacteria cause the 

 injury to the cells or if they enter and grow after the 

 injury is done, the blood cells must fight them as well as 

 repair the damage. Sometimes they cannot do both at 

 once. Then the white blood cells and plasma leave the 

 blood tubes to a still greater degree and lay siege to the 

 bacteria until they 



J a> ^ A 



completely fill the 

 lymph spaces. They 

 even stop up the 

 blood tubes, produc- 

 ing great swelling 

 and pain. White 

 blood cells and bac- 

 teria are now tightly 

 wedged among the 

 injured tissues with 

 no chance for escape 

 and with no nourish- 

 ment. Then the 

 whole injured part 

 becomes soft and 

 finally bursts and 

 runs out as a creamy 

 matter called pus. 

 Thus nature sacrifices a part of the body in order to get 

 rid of the bacteria which threaten to overcome the whole 

 body. Then the white blood cells grow and repair the 

 wound as in clean wounds. A mass of pus in the body is 

 called an abscess. Every abscess or collection of pus is 

 caused by bacteria. 



If bacteria grow upon an open cut, the white blood cells must devote 

 part of their energies to fighting them, and so healing goes on slowly, 



The repair of a wound (X 200). 



a new white blood cells upon the surface of a raw 



spot. 

 b growing white blood cells. 



e older white blood cells which are becoming 

 elongated and branched like connective tissue 

 cells. 



f old capillary sending out a new branch. 



g old connective tissue. 



