PNEUMONIA. 291 



irritant foreign materials accidentally inhaled can cause 

 it. The majority of the cases, however — and especially 

 those which are distinctly peribronchial — are caused by 

 the presence of the staphylococcus and streptococcus of 

 suppuration. Friedlander's bacillus may also aid in pro- 

 ducing local inflammations. 



3. Tubercular Pneumonia. — At times the process of 

 pulmonary tuberculosis is so rapid, and associated with 

 the production of so much semi-liquid, semi-necrotic 

 material, that the auto-infection of the lung is greatly 

 favored ; the tubercle bacilli are distributed to the entire 

 lung or to large parts of it, and a distinct inflammation 

 occurs. Such a pneumonia may be caused by the tubercle 

 bacillus alone, but more often it is aided by accompany- 

 ing staphylococci, streptococci, tetragenococci, pneumo- 

 cocci, pneumobacilli, and other organisms apt to be pres- 

 ent in a lung in which tuberculosis is in progress and 

 ulceration and cavity-formation are advanced. 



4. Mixed Pneumonias. — It frequently happens that 

 pneumonia occurs in the course of, or shortly after the 

 convalescence from, influenza. In these cases a mixed 

 infection is present, and there is no difficulty in deter- 

 mining that both the influenza bacillus and the pneumo- 

 coccus are present. Again, sometimes the pneumococci 

 and staphylococci operate simultaneously, and produce 

 a purulent pneumonia with abscesses as the conspicuous 

 feature. As almost any combination of the described 

 bacteria is possible in the lungs, and as these combi- 

 nations will all produce varying inflammatory conditions, 

 it must be left for the student to imagine what the par- 

 ticular characters of each may be. 



Among these mixed pneumonias may be mentioned 

 those called by Klemperer and Levy "complicating 

 pneumonias," occurring in the course of typhoid, etc. 



