52 CLINICAL BACTERIOLOGY AND HEMATOLOGY 



are special methods of staining which may be used to render the 

 capsule more distinct, but these are usually unnecessary for the 

 diagnosis. 



Interpretation of Results. 



In cases of lobar pneumonia you will probably find pneumococci 

 in great quantity, and no other bacteria in a specimen of sputum 

 )iiade in the manner described. If you find many pneumococci in a 

 case of lobular pneumonia the disease may have been caused by 

 another germ, and the cocci in question may have been nothing 

 more than a secondary infection. A specimen should be stained 

 deeply by carbol fuchsin or methylene blue and searched for 

 bacilli resembling those of influenza, etc., and another should be 

 stained for the tubercle bacillus if the clinical aspect of the case 

 suggests the possibility of a tuberculous origin for the disease. 



Pus is examined in the same way, and presents similar appear- 

 ances. Most of the cocci are extracellular, but some are frequently 

 contained in the cells, and may then not retain Gram's stain. 



It is not usually necessary to make cultures, as the pneumococcus 

 is readily recognized in pathological material from its morphological 

 appearance and staining reactions alone. Where cultures are 

 required, agar is about as good a medium as can be used, and it 

 must be incubated at the body temperature. The colonies are 

 visible after twenty-four hours as very small transparent circular 

 masses, which are but slightly raised and show but little tendency 

 to increase in size on further incubation. It is a very delicate 

 organism, and one which readily dies out on ordinary media, so 

 that if a culture is to be " kept going " it must be transplanted 

 every two or three days to a fresh tube. This is one of its most 

 characteristic features. 



INFLUENZA 



In the first edition of this book, in treating of influenza, I followed 

 the usual teaching of bacteriologists and regarded the disease as a 

 specific one, and as being caused in all cases by the influenza (or 

 Pfeiffer's) bacillus. Recent observations, both in England and on 

 the Continent, have shown that this view can no longer be upheld, 

 unless we greatly restrict the use of the term " influenza," and use 

 it only for those cases in which the bacillus in question is found. 

 This is quite unjustifiable, for the diseases appear to be identical 

 in clinical history ; and in cases in which we should be practically 



