136 CLINICAL BACTERIOLOGY AND HEMATOLOGY 



Weichselbaum's Diplococcus meningitidis intracellularis is now 

 generally considered to be the specific cause of cerebro-spinal 

 fever. It is a diplococcus which varies very considerably in size, 

 but is usually rather smaller than the gonococcus. The opposed 

 surfaces of two cocci making up the pair are usually somewhat 

 flattened, but this is not so marked as in the latter organism. It 

 is often contained within the polynuclear leucocytes, but is not 

 grouped in large numbers in a single cell — others being free— as 

 is usually the case with the gonococcus (see Plate III., where the 

 two organisms are contrasted). The two also differ in their cultural 

 characters and in their pathogenicity to animals. If any question 

 should arise as to which of the two is present in the meningeal 

 exudation in a case in which no cultures have been taken, other 

 evidence of gonorrhoeal infection should be sought for. 



Still's diplococcus of posterior basic meningitis cannot be 

 distinguished from the D. meningitidis by its morphological 

 characters alone, and many bacteriologists think 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 

 meningitis 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 recognised 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.* 



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 to the bottom, and is withdrawn after some hours, spread on a slide, dried 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

 (See also p. 138). 



