PART IV. 



PATHOGENIC BACTERIA. 



Suppuration and Allied Conditions. The occurrence of 

 suppuration is characterized by certain appearances which 

 we are accustomed to describe under the name of inflamma- 

 tion. The study of inflammation belongs to pathology, and 

 cannot be considered here. However, certain evidences 

 which are characteristic of the suppurative variety of inflam- 

 mation need to be outlined on account of their relation to the 

 action of the pyogenic bacteria. 



In a suppurating area, as is well known, the blood-ves- 

 sels are dilated, and the lymph-spaces become filled with 

 serum. Leucocytes are attracted to the neighborhood in 

 large numbers, we may suppose by a positive chemotaxis, 

 and crowd the small veins and capillaries. The leucocytes, 

 by reason of their amoeboid movement, pass through the 

 walls of the vessels at little openings filled with cement- 

 substance, situated between the lining endothelial cells. Ac- 

 cording to the theory of phagocytosis, they are bent on find- 

 ing the irritant which has led to the inflammation, and upon 

 isolating it and rendering it harmless. At the point which 

 appears to be the center of the inflammatory area there is 

 usually, but not always, a necrosis of the cells of the tissue; 

 this constitutes the central slough or the familiar core of 

 some boils. The necrosis is to be attributed to poisons 

 formed by the micrococci. In sections cut through such an 

 abscess the nuclei of the central necrotic cells fail to take 

 the nuclear stain ; the necrotic mass does not stain, or takes 



