502 Pneumonia 



Pneumonia 65.95 



Bronchopneumonia 15.85 



Meningitis 13.00 



Empyema 8.53 



Otitis media 2.44 



Endocarditis 1.22 



Hepatic abscess 1.22 



In 46 consecutive pneumococcus infections of children 

 he found : 



Otitis media 29 



Bronchopneumonia 12 



Meningitis 2 



Pneumonia i 



Pleurisy : i 



Pericarditis i 



Susceptibility. Not all animals are equally susceptible to 

 the action of the pneumococcus. Mice and rabbits are 

 highly sensitive, dogs, guinea-pigs, cats, and rats are much 

 less susceptible, though they may also succumb to the in- 

 oculation of large doses. 



Specificity. The etiologic relationship of the pneumo- 

 coccus to pneumonia is based chiefly upon the frequency of 

 its presence in croupous pneumonia. Netter* found it 82 

 times in 82 autopsies upon such cases; Klemperer, 21 times 

 out of 2 1 cases studied by puncturing the lung with a hypo- 

 dermic syringe. Weichselbaum obtained it in 94 out of 129 

 cases; Wolf, in 66 out of 70; and Pierce, in no out of 121 

 cases. In about 5 per cent, of the cases it remains localized 

 in the respiratory apparatus; in 95 per cent., it invades the 

 blood. An interesting paper upon this subject has been 

 written by E. C. Rosenow.f 



The conditions under which it enters the lung to produce 

 pneumonia are not known. It is probable that some sys- 

 temic depravity is necessary to establish susceptibility, and 

 in support of this view we may point out that pneumonia is 

 very frequent, and exceptionally severe and fatal, among 

 drunkards, and that it is the most frequent cause of death 

 among the aged. Whether, however, any particular form of 

 vital depression is necessary to predispose to the disease, 

 further study will be required to tell. 



Virulence. Pneumococci vary greatly in virulence, and 

 rapidly lose this quality in artificial culture. When it is 



* "Compte-rendu," 1889. 



f "Jour. Infectious Diseases," 1904, i, p. 280. 



