ALLIED DIPLOCOCCI 247 



many cases rich in immune-bodies for the meningococcus, and 

 possessing a greatly increased bactericidal action as compared 

 with normal serum. Though the number of cases treated by 

 this method is not yet large, a distinctly favourable result has 

 been obtained. 



Allied Diplococci. In the naso-pharynx there occur other 

 Gram-negative diplococci which have j a close resemblance to 

 the diplococcus 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 leuco- 

 cytes. Its colonies on serum agar are more opaque than those 

 of the diplococcus intracellularis, and often have a somewhat 

 firm though friable 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. The diplococcus pharyngis 

 mccus (v. Lingelsheim) also grows at room temperature, and its 

 colonies are very tough and adhere to the surface of the medium ; 

 it can thus readily be distinguished from the meningococcus. It 

 has marked fermentative properties, acting on glucose, maltose, 

 saccharose, and laevulose. The diplococcus mucosus has colonies 

 of slimy consistence ; it grows at room temperature, and it forms 

 capsules, which can be demonstrated by the method of Hiss. 

 There are other Gram-negative diplococci which are chromogenic, 

 and thus can readily be distinguished. The points of difference 

 between the meningococcus and the gonococcus are given on 

 p. 252. A Gram-positive diplococcus called the diplococcus 

 crassus is also of common occurrence; it is rather larger than 

 the diplococcus intracellularis, and especially in sub-cultures may 

 tend to assume staphylococcal forms. 



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 



