EPIDEMIC CEREBRO-SPINAL MENINGITIS 217 



found that it had a certain protective effect in guinea-pigs and 

 monkeys against infection by the organism, but, on the whole, 

 better results were obtained with the serum of inoculated 

 monkeys. As yet no important applications towards the 

 treatment of the disease have been effected. 



In the nasal cavity there occur other diplococci which have a 

 close resemblance to the diplococous intracellularis. These occur 

 in the healthy state but are especially abundant in catarrhal 

 conditions ; of these the diplococcus catarrhalis has the closest 

 resemblance to the diplococcus intracellularis. In addition to 

 occurring in health this organism has also been found in large 

 numbers in epidemic catarrh. Its microscopic appearances are 

 practically similar to those described above, and it also occurs 

 within leucocytes. Its colonies on serum agar are more opaque 

 than those of the diplococcus intracellularis, and they have a 

 tough consistence, so that they are sometimes removed en masse 

 by the platinum needle. The organism grows on gelatin at 

 20 C. without liquefying the medium, and it has none of the 

 fermentative properties described above as belonging to the 

 diplococcus intracellularis. Other species of Gram - negative 

 micrococci have also been isolated, and a Gram-positive diplo- 

 coccus called the diplococcus crassus is of common occurrence 

 this organism is rather larger than the diplococcus intracellularis, 

 and especially in sub-cultures may tend to assume staphylo- 

 coccal forms. It is thus evident that the nasal cavity is the 

 common habitat for a number of closely allied diplococci, and 

 that the identification of any suspected organism as the diplo- 

 coccus intracellularis can only be effected by cultivation tests. 



Apart from the epidemic form of the disease, meningitis may 

 be produced by almost any of the organisms described in the 

 previous chapter, as associated with inflammatory conditions. 

 A considerable number of cases, especially in children, are due 

 to the pneumococcus. In many instances where no other lesions 

 are present the extension is by the Eustachian tube to the middle 

 ear. In other cases the path of infection is from some other 

 lesion by means of the blood stream. This organism also infects 

 the meninges not infrequently in lobar pneumonia, and in some 

 cases with head symptoms we have found it present where there 

 was merely a condition of congestion. The pneumobacillus also 

 has been found in a few cases. Meningitis is not infrequently 

 produced by streptococci, especially when middle ear disease is 

 present,- less frequently by one of the staphylococci ; occasionally 

 more than one organism may be concerned. In meningitis 

 following influenza the influenza bacillus has been found in a 



