PATHOGENIC BACTERIA. 235 



bacteria, which can be demonstrated by cultivation, and, as 

 a rule, also in smears made and stained upon cover-glasses. 

 The bacteria are generally found outside the pus-cells. In the 

 case of the gonococcus and the Diplococcus intraceUularis men- 

 ingitidis they are characteristically found in pairs, inside of, 

 or at least attached to, the pus-cells. The character of the 

 suppuration differs somewhat with the different species of pyo- 

 genic bacteria. The kind of abscess above described — local- 

 ized and having a central slough, usually rather slow in pro- 

 gress — is typical for the Staphylococcus pyogenes aureus, which 

 is prone to produce circumscribed areas of suppuration. The 

 Streptococcus pyogenes, on the other hand, oftener leads to 

 suppuration of a more diffused character, such as we see in 

 cellulitis and erysipelas; but either organism may, at times, 

 produce the effects usually characteristic of the other. Pus 

 having a blue or green tinge generally owes the color to the 

 presence of the Bacillus pyocyaneus. The commonest pus- 

 producing organism is then the Staphylococcus pyogenes au- 

 reus, and next to that the Streptococcus pyogenes. Among the 

 other pyogenic bacteria the following may be named: 



Staphylococcus pyogenes albus, including Staphylococcus 

 epidermidis albus; streptococcus of erysipelas (probably iden- 

 tical with Streptococcus pyogenes) ; gonococcus; Diplococcus 

 intraceUularis meningitidis; Staphylococcus pyogenes citreus; 

 Micrococcus tetragenus; Micrococcus pyogenes tenuis, which 

 may be the same as the Micrococcus lanceolatus; Staphylo- 

 coccus cereus albus and flavus. 



Pus-formation may also be due to Micrococcus lanceolatus. 

 Bacillus pyocyaneus. Bacillus proteus, Bacillus coK communis. 

 Bacillus pyogenes foetidus. Bacillus pneumoniae (of Friedlander), 

 Bacillus aerogenes capsulatus, the ray fungus of actinomycosis, 

 and possibly the bacillus of bubonic plague. Besides these 

 organisms, there are others whose effects are usually more 

 marked in a specific way which sometimes form pus, as the 



