156 CLINICAL BACTERIOLOGY AND HEMATOLOGY 



distinguished from the D. meningitidis by its morphological 

 characters alone ; it is now considered that the two organisms 

 are in reality identical. The truth seems to be that the organism 

 which we call the meningococcus is a very variable one, some 

 forms being much more easily cultivated than others, and also 

 differing in a few other minute points. Yet these forms appear 

 to occur indiscriminately in true epidemic cerebro-spinal menin- 

 gitis and in posterior basic meningitis, and these diseases are 

 quite indistinguishable on pathological grounds. 



The Rarer Causes of Meningitis. — The bacilli of typhoid fever, 

 anthrax, influenza, etc., may also be recognized in the methylene 

 blue specimen, and should be identified (if possible) by a careful 

 study of their morphological appearances and reaction to Gram's 

 stain. 



If no organisms are found in the methylene blue specimens 

 after a careful search, and if the characters of the fluid are such 

 as indicate that meningitis is present, the presumption is that the 

 case is one of tuberculous meningitis. Films should be stained 

 in the method already described and carefully searched ; the 

 bacilli are present in very scanty numbers, and many films may 

 have to be examined before one is found (see also p. 157).* 



Cultural Examination. — ^The tubes which have been inoculated 

 by allowing the fluid to drop directly on to the surface of the 

 medium are to be incubated for twenty-four hours at the body 

 temperature. Streptococci, staphylococci, pneumococci, and the 

 rarer organisms, will probably have developed by this time, and 

 will have formed colonies such as have been previously described. 

 Weichselbaum's diplococcus forms (on blood-serum) " round, 

 whitish, shining, viscid-looking colonies, with smooth, sharply 

 defined outlines which attain a diameter of i to i\ millimetres 

 in twenty-four hours." The colonies on agar are similar, but 

 slightly larger, and the growth may become confluent. 



If no colonies appear on blood-serum or agar at the end of 

 forty-eight hours, the case is probably due to the tubercle bacillus 

 or the gonococcus. In some cases of cerebro-spinal fever the 

 diplococci in the exudate are all dead, and cultures remain sterile. 



* Lenharz adds a shred of clean cotton- wool to the fluid. This sinks slowly 

 to the bottom, and is withdrawn after some hours, spread on a slide, dried, 

 and stained for tubercle bacilli. The author has had no experience of this 

 method, but Mr. Leedham-Green informs him that it is of considerable value. 



