EXPERIMENTAL INOCULATION 645 



pharynx to the meninges. During an epidemic of meningococcal cerebro-spinal 

 meningitis it is therefore a matter of great importance that the naso-pharynx 

 of contacts should be examined for the presence of the Meningococcus : a 

 person may carry the organism in his naso-pharynx and spread the infection 

 while himself remaining in apparently good health. Indeed Bruns and Hohn 

 venture the opinion that there are ten to twenty times more carriers of the 

 Meningococcus than cases of meningitis. On an average the Meningococcus 

 remains in the pharynx of a " carrier " for about a fortnight, though it may 

 persist for several months. 



Meningococcus and Gonococcus. Many observers have drawn attention 

 to the close resemblance which exists between the Meningococcus and the 

 Gonococcus, e.g. their microscopical appearances, reaction to Gram's stain, 

 intra-cellular position within the leucocytes and agglutination by the same 

 specific serums. 



It has however been shown that these two organisms though they belong 

 to the same group are nevertheless two sharply differentiated species : the 

 Meningococcus is pathogenic for mice while the Gonococcus is not, and the 

 cultural characteristics of the two cocci are different : Zupnik by inoculating 

 cultures of the second generation of the Meningococcus into the urethra of 

 five medical men in good health failed in every case to produce symptoms of 

 gonorrhoea, while if a gonococcus even of the twentieth generation be simi- 

 larly inoculated symptoms of gonorrhoea follow. Finally the two organisms 

 can be shown to be different species by a study of the agglutination and 

 complement fixation reactions. 



SECTION I. EXPERIMENTAL INOCULATION. 



The virulence of the Meningococcus is subject to considerable variation 

 but in any case it is only slightly pathogenic for laboratory animals 



Mice are the most susceptible animals : they generally succumb after intra- 

 peritoneal inoculation of a large dose of culture. Post mortem examination 

 reveals a condition of peritonitis, and in the exudate the micro-organisms will 

 be found to be present in very large numbers ; the spleen and the heart blood 

 contain very few. 



Rabbits and especially guinea-pigs are less susceptible : they only suc- 

 cumb after the inoculation, intra-peritoneally or intra-venously, of very 

 large doses of cultures. In these animals metastatic deposits do not occur 

 and the organism does not multiply ; death results from intoxication 

 (Weichselbaum, Jundell). In mice on the other hand some slight degree of 

 multiplication seems to take place but successive passages never lead to any 

 increase in virulence (Bettencourt and Franca). 



Inoculation into the meninges of laboratory animals does not lead to 

 symptoms of meningitis (Weichselbaum, Albrecht and Ghon). But in 

 monkeys, Flexner produced a true meningitis fatal in 24 hours by inoculating 

 the Meningococcus beneath the arachnoid : post mortem, the lesions typical of 

 cerebro-spinal meningitis were found. 



SECTION II. MORPHOLOGY. 

 1. Microscopical appearance. 



In meningeal exudates and in the cerebro-spinal fluid the Meningococcus 

 generally occurs as a diplococcus. The elements composing the diplococcus 

 resemble coffee beans, the flattened surfaces being opposed to each other. 

 The micro-organism is very similar to the Gonococcus in appearance : not 



