588 ELECTIVE LOCALIZATION OF BACTERIA 



A striking example of the extreme specificity of the streptococcus and a shifting 

 of this property under certain conditions was found in experiments performed in a 

 series of cases presenting varying degrees of neuro-myelo-encephahtis which occurred 

 during and after an epidemic of hiccup/ LocaHzation with lesions, in locations strik- 

 ingly like those in the patient, occurred in animals injected with material from the 

 nasopharynx or tonsil. The study was a striking example in which the changing char- 

 acter in an epidemic was closely simulated in the experimental animal. 



In another series of experiments, believed to be of epidemiological importance, 

 the streptococcus of epidemic encephalitis was made to resemble the streptococcus 

 isolated so constantly during the pandemic of influenza of 1918.^ On isolation it had 

 little or no eflfect on intratracheal insufflation, but had marked neurotropic properties 

 manifested on intracerebral, intravenous, and intraperitoneal injection and following 

 packing of the nose of rabbits and monkeys with gauze soaked in the culture. After 

 successive passage through animals it became highly virulent, produced meningitis on 

 intracerebral injection and the symptoms, with sharp reduction in the leukocyte count 

 and lesions of the lung, of influenza as they occur in epidemic waves (pneumotropic 

 phase). Both neurotropic and pneumotropic properties were lost after prolonged cul- 

 tivation on artificial media. 



GENERAL DISCUSSION AND CONCLUSIONS 



It is uncertain whether the streptococci isolated in each of the many diseases 

 studied, and which manifested such widely different elective localizing powers on iso- 

 lation, are distinct varieties or modifications of a single strain. They all belonged to the 

 pneumococcus-streptococcus group and were much alike in morphology and cultural 

 reaction. Nearly all produced a greenish zone of hemolysis surrounding small grayish 

 colonies on horse-blood-agar plates. A few were indifferent to blood agar, and a few 

 produced a narrow zone of clear hemolysis. The usual fermentation reactions in 

 sugars were variable and of little value in classification. The cultural features were 

 quite stable under ordinary methods of cultivation. Mutational forms occasionally 

 developed when cultured under conditions of stress, both in vitro and in vivo. Their 

 general virulence was relatively low. Intraperitoneal injections rarely caused death 

 from peritonitis and intravenous injection rarely caused death from bacteremia. Ag- 

 glutination and precipitation reactions were highly specific with freshly isolated strains 

 in some of the diseases studied. This was often lost soon after cultivation on artificial 

 media as was also the elective localizing power, but not in a strictly parallel manner. 

 Elective localizing power of the streptococci tended to disappear quickly when culti- 

 vated on artificial media and more slowly on passage through animals. A shift in the 

 powers of localization was often noted under these conditions, comparable to those 

 noted in the studies on transmutation in the pneumococcus-streptococcus group. 

 Elective localizations of the streptococci isolated were especially marked during acute 

 exacerbations of chronic conditions, and in acute cases, especially during the winter 

 months when respiratory infections were prevalent and an increased incidence of sys- 

 temic conditions prevailed. The fact that exacerbations and acute attacks such as 



' Rosenow, E. C: Arch. Neurol, b' Psychiat., 16, 21. 1926. 



»Rosenow, E. C: /. Infect. Dis., 33. 531. 1923. 



