302 PATHOGENIC BACTERIA. 



and rabbits are highly sensitive to the operations of the 

 organism ; dogs are comparatively immune. 



From this brief review of the peculiarities of the pneu- 

 mococcus it must be obvious that its reputation in pneu- 

 monia depends more upon the regularity with which it is 

 found in that disease than upon its capacity to produce a 

 similar affection in the lower animals. 



As in numerous other diseases, we are unable to furnish 

 an absolute proof of specificity according to the postu- 

 lates of Koch. 



The disease is peculiar in that recovery from it is fol- 

 lowed either by no immunity or by one of such brief dura- 

 tion as to allow of frequent relapses ; and it is well known 

 that many cases show a subsequent predisposition to 

 fresh attacks of the disease. This brevity of immunity 

 lessens the probability that in the future we shall dis- 

 cover an antitoxin that shall be powerful in its influ- 

 ence upon the course and termination of the disease. 



The experiments of the Klemperers showed that the 

 serum of immunized rabbits protected other animals, 

 and excited our interest a few years ago ; they, how- 

 ever, failed when the principle was applied in human 

 medicine, and the treatment of pneumonia by the in- 

 jection of blood-serum from convalescents has been 

 given up as useless and dangerous. 



The pneumococcus is pathogenic in other ways than 

 by the production of croupous pneumonia ; thus, Foa, 

 Bordoni-Uffreduzzi, and others have found it in cerebro- 

 spinal meningitis ; Frankel, in pleuritis ; Weichselbaum, 

 in peritonitis ; Banti, in pericarditis ; numerous observers 

 have found it in acute abscesses ; Gabbi has isolated it 

 from a case of suppurative tonsillitis ; and Zaufal, Levy, 

 and Schrader and Netter have been able to demonstrate 

 its presence in the pus of otitis media. It has also been 

 reported as occurring in the joints in arthritis following 

 pneumonia. 



The pneumococcus no doubt is habitually present in 

 the mouth of almost every healthy person. Its entrance 



