MICROCOCCUS INTRACELLULARIS MENINGITIDIS 515 



Diplococcus intracellularis meningitidis was first seen in menin- 

 geal exudates by Marchiaf ava and Celli 2 in 1884. These authors 

 not only described accurately the morphological characteristics now 

 recognized, but also called attention to the intracellular position of 

 the microorganism and to its gonococcus-like appearance. They 

 failed, however, to cultivate it. 



Observations confirmatory of the Italian authors were, soon after, 

 made by Leichtenstern. 3 Cultivation and positive identification as a 

 separate species was not accomplished, however, until Weichsel- 

 baum, 4 in 1887, reported his observations upon six cases of epidemic 

 cerebrospinal meningitis in which he not only found the cocci mor- 

 phologically, but was able to study their biological characteristics in 

 pure culture. The researches of Weichselbaum were soon confirmed 

 and extended by elaborate studies 5 which left no doubt as to the 

 specific relationship between the microorganism cultivated by him 

 and the clinical condition. 



Morphology and Staining. Stained in the spinal fluid from an 

 infected patient, the meningococcus bears a striking similarity to 

 the gonococcus. The microorganisms appear intra- and extracellu- 

 larly, usually in diplococcus groups, sometimes as tetrads, or even in 

 larger agglomerations. The individual diplo-forms are flattened on 

 the sides facing each other, presenting somewhat the biscuit-form 

 of the gonococcus. The variation in size of the cocci in the same 

 smear is a noticeable feature and of some diagnostic importance. 

 This dissimilarity in size is noticeable also in cultures, which, 

 especially when older than twenty-four hours, contain forms double 

 or even triple the size of the average coccus. These may possibly be 

 involution forms. 



The meningococcus is non-motile and non-spore forming. It 

 stains easily with all the usual aqueous anilin dyes. Its behavior 

 toward Gram's stain was long a subject of controversy, owing to 

 the error of Jaeger, 6 who claimed to have found it Gram-positive. 

 There is no question now, however, that the cocci decolorize by 

 Gram's method when this is carefully carried out. 



2 Marchiaf ava and Celli, Gaz. degli ospedali, 8, 1884. 



3 Leichlenstern, Dent. med. Woch., 1885. 



4 Weichselbaum, Fort. d. Med., 1887. 



5 Councilman, Mallory, and Wright, Special Eep. Mass. Board of Health, 1898, 

 Albrecht und Ghon, Wien. klin. Woch., 1901. 



6 Jaeger, Zeit. f. Hyg., xix, 1895. 



