226 PUBLIC HEALTH BACTERIOLOGY 



Products. No soluble toxin yet isolated ; endotoxin 

 by freezing and grinding. 



Pathogenicity. For mice and rabbits, very great ; for 

 guinea-pigs, less ; for man, medium. Susceptibility is 

 characterized by general septicsemic infection ; resistance 

 by occurrence of localized processes, e.g., in man : acute 

 lobar pneumonia, pleurisy, empyema, pericarditis, menin- 

 gitis, otitis media, etc. 



Isolation. Inoculate a mouse at the root of the tail with 

 a little of the suspected material. The animal dies in 24 

 hours, and its blood is swarming with typical, encapsuled 

 lance-shaped diplococci, if pneumococci present. 



Immunity. Agglutinins are formed, and agglutination is 

 observed in 1-40 to 1-50 dilution with serum from pneu- 

 monic patient, and most marked at time of crisis. Passive 

 immunization with sera has been unreliable so far. A 

 leucocyte extract with water has given encouraging results. 



Resistance. Has been found alive in dried sputum 

 after 55 days. Ten minutes at 52 C. is fatal. Very 

 sensitive to weak solutions of disinfectants, but not in 

 sputum. 



STREPTOCOCCUS MUCOSUS. 



This organism has been isolated from cases of menin- 

 gitis, peritonitis, phlebitis, and parametritis, and from 

 certain cases of pneumonia. It shows a marked tendency 

 to form chains, but often appears in diplococcus 

 forms. It is also capsulated, but never lance-shaped. It 

 reacts to sugars as does the pneumococcus. It is patho- 

 genic to white mice, but not so markedly to the rabbit as 

 the pneumococcus. Growths are similar. It excites the 

 formation of weak agglutinins, which can also in some 

 cases agglutinate pneumococci. Also anti-pneumococcic 

 serum frequently agglutinates it. These facts suggest a 

 group relationship. 



MENINGOCOCCUS. 



First described by two Italian observers in 1884, 

 but first cultivated by Weichselbaum from cases of 

 cerebrospinal meningitis in 1887. It is a small coccus, 

 very like the gonococcus, and like it occurring in pairs, 



