CONGESTION AND IMFLAMMATION 207 



this case, by the outpouring of plasma and white blood 

 corpuscles (leucocytes) through the capillary walls into the 

 lymph spaces. This extraordinary flow is due to changes 

 in the cement which holds together the capillary cells com- 

 posing the walls, and may in some instances be accompanied 

 by the outpoming of red corpuscles. 



In simple injuries the result of this outpouring of plasma 

 is to stick together the old cells and cause them to grow and 

 unite, while the leucocytes and injured cells are absorbed 

 and the injury thus repaired. 



If, however, the injuiy is extensive or bacteria are in- 

 troduced into the injured area, a more extensive action is 

 involved. The growth of the bacteria or the nature of the 

 injury may cause the death of other cells in the neighbour- 

 hood, and the formation of a mass of dead tissue results. 

 In this event the white corpuscles proceed to kill or absorb 

 the bacteria and dead tissue cells with the formation of a 

 mass of matter usually designated as pus. At the same 

 time new cells are formed and a new tissue grows in place 

 of the old one. This pus may be removed by the lympha- 

 tics or absorption into the blood vessels, or it may soften 

 the tissue about it and discharge, as in an abscess. In 

 the latter event, the white corpuscles either devour the 

 bacteria and cells, or give off ferments which dissolve them. 

 Meanwhile the living cells about the injured part are ex- 

 c'ted to growth and reproduction, and thus new cells pro- 

 duced which unite and replace the old tissues. 



The processes here are evidently two, the dissolving 

 and removal of old matter through the agency of the white 

 corpuscles, and the formation of new tissue cells to replace 

 the injured ones. The manner in which the old matter is 

 removed varies with the location of the injury. These 



