PNEUMOCOCCUS 65 



body. It is believed that pneumococci which have been present in the mouth, 

 nose or throat for aconsiderable time without producing any ill effect, cah sud- 

 denly become virulent and cause pneumonia. Pneumonia caused by this 

 organism ordinarily is not contagious, but at times there occur small epidemics 

 that seem to indicate a high degree of contagiousness. Some epidemics of 

 pneumonia caused by the pneumococcus are strikingly more fatal than others. 

 None of these phenomena have been explained. 



It is claimed by some that the pneumococcus is the offending organism in 

 90 per cent, of all cases of acute lobar pneumonia and in from 50 to 80 per cent, 

 of all other forms of pneumonia. It is an established fact that the pneumococcus 

 is the most common cause of pneumonia, but the figures given are probably 

 too high. 



In pneumonia the organism is present in the sputum and can frequently be 

 obtained from the peripheral blood. 



The pneumococcus is frequently the cause of otitis media, sometimes the 

 cause of rhinitis and ozena, pleurisy, peritonitis, endocarditis, pericarditis and 

 meningitis. If present in the lachrymal secretion at a time when trauma or 

 operation causes a breach in the cornea or sclera, a serious infection often 

 ensues. 



When injected subcutaneously into rabbits a localized area of inflammation 

 with much edema or suppuration at the point of inoculation may be the only 

 effect, more commonly a fatal septicemia and death within 48 hours is the 

 result. Under certain conditions, lobar pneumonia has been produced by spray- 

 ing pneumococci into the lungs of rabbits and dogs. 



Diagnosis. In pneumonia microscopic examination of the sputum fre- 

 quently is the only procedure required to establish the bacteriological diagnosis; 

 blood culture is sometimes required and is carried out in detail as described for 

 streptococci. 



In localized lesions, such as pleurisy, the organism is found in the exudate. 

 In meningitis the pneumococci are found in the spinal fluid. 



In their efforts to produce a therapeutic serum, Dochez, Avery, Cole and 

 others recently disclosed numerous important facts relative to pneumococci and 

 pneumonia. They have shown that organisms identical in morphology, stain- 

 ing and cultural characteristics may be divided, by agglutination tests, into four 

 groups or types that differ in distribution, pathogenicity and susceptibility 

 to immune serum. Experiments have shown that among the various animals 

 treated with these organisms horses produce the most effective therapeutic sera, 

 and that the active principle of such sera is confined to the globulin portion. 



Animals inoculated with Type I pneumococci yield serum which agglutinates 

 Type I organisms but does not agglutinate any others; those inoculated with 

 Type II pneumococci yield serum that agglutinates Type II organisms but does 

 not agglutinate any others, animals inoculated with Type III pneumococci 

 yield serum which cannot agglutinate Type III organisms until they have been 

 divested of their capsule; and does not agglutinate any other organisms. 



Type IV really is not a type it is a heterogeneous group to which is rele- 



