THE PLEURA 



143 



streptococci or pneumococci are found the inflammation is likely 

 to pass on into suppuration. The great majority of these cases 

 of " simple" acute pleurisy are really due to the tubercle bacillus, 

 but their true nature is difficult to determine except by inoculation 

 experiments. A cytological examination of the fluid should be 

 made, and in tuberculous cases the cells present will usually be 

 found to be lymphocytes, with an occasional admixture of blood- 

 corpuscles (see p. 257). 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 ordinary way ; 

 but they are not always found even in true cases of tuberculous 

 pleurisy. Where the fluid coagulates spontaneously, 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. HCl) until completely 

 dissolved. The resulting fluid is now centrifugalized or allowed 

 to stand for a day or so (in which case some thymol should be 

 added to prevent excessive growth of bacteria), and films prepared 

 from the deposit, which will contain the tubercle bacilli. The 

 advantage 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 digestion 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, strepto- 

 cocci, staphylococci, and the tubercle bacillus. 



The pneumococcus is readily demonstrated by a microscopical 

 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 go per cent. 



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



