OCCURRENCE OF CAUSATIVE AGENTS. 141 



pleural fluid obtained under sterile conditions, and to wait 

 and see whether the animals die of tuberculosis or not. 

 This procedure, however, always occupies several weeks, 

 and even then it is not always entirely reliable, and it fre- 

 quently fails to resolve the doubt, as in spite of an evident 

 tuberculous origin of the pleuritic effusion the animals often 

 remain well. The reason for this is to be found in the 

 small number in which the tubercle-bacilli are usually 

 present in the effusion. It is, therefore, advisable to centrif- 

 ugate a considerable amount of the effusion, and to inocu- 

 late guinea-pigs with the precipitate thus obtained. 



Bacteriologic examination is, however, much more im- 

 portant in the diagnosis of empyema. If the agar-tubes 

 inoculated with the pleural pus remain sterile, this indicates 

 that the process is, in all probability, tuberculous. Direct 

 microscopic demonstration of tubercle-bacilli in cover-glass 

 preparations is, however, successful only in a few cases. 

 Not rarely the empyema of tuberculous subjects is due to 

 secondary infection. 



Various observers have reached conclusions with regard 

 to both the prognosis and the treatment of empyema from 

 the species and the virulence of the bacteria found in the 

 pleural pus. The presence of the diplococci is believed to 

 indicate a much more favorable prognosis than that of the 

 other pyogenic organisms. In this so-called pneumococcus- 

 empyema less radical treatment is therefore necessary. 

 Thoracotomy would, under these circumstances, be super- 

 fluous, simple evacuation by puncture being sufficient. 

 It can actually be admitted that the prognosis of pneumo- 

 coccus-empyema is usually good. Nevertheless, radical 

 operation is indicated if the effusion is not quickly absorbed 

 spontaneously, or at least after puncture. Too much reli- 

 ance is not to be placed upon spontaneous attenuation of 

 the bacteria in the pus, or upon their death, although the 

 organisms in question live usually only for a short time in 

 artificial culture. Bacteria with fully preserved virulence have 

 been cultivated from pleural pus after the lapse of as long 

 as three and one-half months. Further, recovery from em- 

 pyema due to staphylococci, streptococci, and even typhoid 

 bacilli, has been reported in isolated instances as occurring 

 spontaneously or after simple puncture. The question is 

 yet uudecided whether operation should be undertaken for 

 the relief of purulent effusions in tuberculous subjects when 



