164 RELATIONS OF BACTERIA TO DISEASE. 



We shall first consider the effects of bacteria on the body 

 generally, and afterwards the nature of the chemical products. 



EFFECTS OF BACTERIAL ACTION. 



These may be for convenience arranged in a tabular form 

 as follows : 



A. Tissue Changes. 



(1) Local changes, i.e. changes produced in the neigh- 



bourhood of the bacteria. 

 Position (a] At primary lesion. 

 (&) At secondary foci. 



Character (a) Tissue reactions 1 Acute or 



(b) Degeneration and necrosis j Chronic. 



(2) Produced at a distance from the bacteria, directly 



or indirectly, by the absorption of toxins. 



(a) In special tissues 



(a) as the result of damage, e.g. nerve cells 

 and fibres, secreting cells, vessel walls, 

 or 



(/3) changes of a reactive nature in the blood- 

 forming organs. 



(b) General anatomical changes, the effects of mal- 



nutrition or of increased waste. 



B. Changes in Metabolism. 



The occurrence of fever, of errors of assimilation and 

 elimination, etc. 



A. Tissue Changes produced by Bacteria. The effects of 

 bacterial action are so various as so include almost all known 

 pathological changes. However varied in character, they may 

 be classified under two main headings (a) those of a degen- 

 erative or necrotic nature, the direct result of damage, and (b} 

 those of reactive nature, defensive or reparative. The former are 

 the expression of the necessary vulnerability of the tissues, the 

 latter of protective powers evolved for the benefit of the organism. 

 In the means of defence, both leucocytes and the fixed cells of 

 the tissues are concerned. Both show phagocytic properties, i.e. 

 have the power of taking up bacteria into their protoplasm. The 



