THE PLEURA I/ 1 



puscles (see p. 291). If the fluid does not clot spontaneously, 

 it may be very thoroughly centrifugalized, and films prepared 

 from the deposit and stained for tubercle bacilli in the ordin- 

 ary way; but they are not always found even in true cases of 

 tuberculous pleurisy. Where the fluid coagulates spontane^ 

 ously, the best plan is to allow the clot to retract until it has 

 shrunk to a small volume, to remove it from the rest of the 

 fluid, allowing all that will to drain away and then to digest 

 the fibrinous mass in an artificial digestion mixture (pepsin 

 and 0-2 per cent. HC1) until completely dissolved. The re- 

 sulting fluid is now centrifugalized or allowed to stand for a 

 day or so (in which case some thymol should be added to pre- 

 vent excessive growth of bacteria) and films prepared from 

 the deposit which will contain the tubercle bacilli. The ad- 

 vantage of this method is that all the bacilli in four or five 

 ounces of pleuritic fluid may be entangled in the clot and con- 

 centrated into a comparatively small bulk. The tubercle 

 bacilli resist peptic dig*estion for a long time, but other 

 organisms do not, and the method is not available for them.* 



PURULENT pleurisies (empyemata) may be caused by many 

 organisms, the most common being' the pneumococcus, 

 streptococci, staphylococci, and the tubercle bacillus. 



The pneumococcus is readily demonstrated by a micro- 

 scopical examination, the method to be employed being the 

 same as that previously described. 



The pus in these cases is thick and creamy, and of a greenish 

 colour; after it has stood for some time a thin layer of a 

 greenish fluid appears upon the surface. 



When an empyema is due to the pneumococcus alone, no 

 other organisms being present, the prognosis is distinctly 

 better than in cases in which other organisms are present, and 

 the patient often recovers after simple aspiration. This is 

 especially the case in children, in whom empyema is due to 

 this organism in a very large number of cases, certainly over 

 90 per cent. 



If cultures are made in pneumococcic cases, it may be noted 

 that occasionally very few of the organisms appear to grow 

 into colonies, as far as can be judged by a comparison be- 

 tween the numbers of cocci present in the films and of colonies 

 on the tubes. This indicates that the majority of cocci are 

 * Other methods are given on p. 74. 



