212 THE ACUTE PNEUMONIAS 



however, that as the crisis approaches in a case which is to 

 recover the opsonic index rises, and after defervescence gradually 

 falls to normal. And further, as bearing on the factors in- 

 volved in the successful resistance of the organism to the 

 pneumococcus, it has been noted that avirulent pneumococci are 

 more readily opsonised than more virulent strains. Further 

 observations along such lines are to be looked for with interest, 

 and it may be said that Wright's vaccination methods have been 

 applied to the treatment of pneumonia cases, and in certain 

 instances are said to have been followed by favourable result. 

 It may be noted here, in conclusion, that in man it is probable 

 that immunity against pneumonia may be short-lived, as in a 

 good many cases of pneumonia a history of a previous attack is 

 elicited. 



Agglutination of the Pneumococcus. If a small amount of a 

 culture of Fraenkel's pneumococcus be placed in an anti-pneumo- 

 coccic serum, an aggregation of the bacteria into clumps occurs. 

 Such an agglutination, as it is called, is frequently observed 

 under similar circumstances with other bacteria. The pheno- 

 menon is not invariably associated with the presence of protective 

 bodies in a serum, but it has been used for diagnostic purposes 

 in the differentiation of sore throats due to pneumococcus 

 infection from those due to other bacteria. Whether the method 

 is reliable has still to be proved. 



Methods of Examination. These have been already 

 described, but may be summarised thus : (1) Microscopic. 

 Stain films from the densest part of the sputum or from 

 the area of spreading inflammation in the lung by Gram's 

 method and by carbol-fuchsin, etc. (pp. 99, 101), in the latter 

 case without decolorising the groundwork of the preparation. 



(2) By cultures, (a) Fraenkel's pneumococcus. With similar 

 material make successive strokes on agar, blood agar, or blood 

 serum. The most certain method, however, is to inject some 

 of the material containing the suspected cocci into a rabbit. If 

 the pneumococcus be present the animal will die, usually within 

 forty-eight hours, with numerous capsulated pneumococci in its 

 heart blood. With the latter inoculate tubes of the above media 

 and observe the growth. In some cases of severe pneumococcic 

 infection the organism may be cultivated from the blood obtained 

 by venesection (p. 68). (b) Friedldnder's pneumobacillus can 

 be readily isolated either by ordinary gelatin plates or by 

 successive strokes on agar media. 



