CHAPTER XXII 



PATHOGENIC BACTERIA (Continued) 



Mode of Action of Pathogenic Bacteria. Pathogenic 

 bacteria produce morbid conditions in the animal body by the 

 following general methods. Frequently there is a combina- 

 tion of two or more of the methods in one disease condition 

 in the body. 



(a) By mechanically clogging the capillaries of the blood 

 vessels, thus preventing the oxygen and nutriment from reach- 

 ing the vital tissue cells. In anthrax, which is caused by 

 Bact. anthracis, a large portion of the pathogenesis is pro- 

 duced by this mechanical method. Mycotic emboli are often 

 formed in the capillaries. 



(b) By the production of soluble toxins or poisons by the 

 action of bacteria inside the body, which when absorbed by 

 the blood, lymphatics, or nerve tissue and carried to the 

 various cells of the body produce morbid changes within 

 them. In diphtheria, for example, the toxins generated by 

 Bact. diphtheriae are responsible for the disease. 



(c) By the destruction of tissue cells at the focus of the 

 infection, thus incapacitating these cells from performing their 

 normal functions. In tuberculosis, the destruction of tissue 

 by Bact. tuberculosis is one important part of the disease 



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