PNEUMONIA. 355 



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, pneurnobacilli, 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. 



