TISSUE CHANGES PRODUCED BY BACTERIA 181 



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. 

 (b) At secondary foci. 



Character : (a) Tissue reactions I Acute or 



(b) Degeneration and necrosis f 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 



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

 forming tissues and organs. 



(6) General anatomical changes, the effects of 

 malnutrition or of increased waste. 



B. Symptoms and 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 to include almost all known 

 pathological changes. However varied in character, they may 

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

 tive 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 

 cells are guided towards the focus of infection by chemiotaxis, 

 and thus we find that different bacteria attract different cells. 

 The \ most rapid and abundant supply of phagocytes is seen in 

 the case of suppurative conditions where the neutrophile leuco- 

 cytes of the blood are chiefly concerned. When the local lesion 

 is of some extent there is usually an increase of these cells 



