250 THE ACUTE PNEUMONIAS 



the bacterial cells, which are thus rendered more pervious to the 

 serum constituents. There is evidence, however, that the protein 

 constituents of sera exercise an inhibitory effect on the lytic 

 action of the soaps, and Lamar has made the interesting observa- 

 tion that this inhibitory action can to a certain extent be 

 neutralised by the use of boric acid. These observations are of 

 the highest importance, and there is some experimental evidence 

 that they may form the basis for a therapeutic treatment of 

 pneumococcic infections. That they have a bearing on the 

 explanation of natural recovery from such infections is indicated 

 by the fact that in inflammatory exudations soaps form a definite 

 constituent. 



Agglutination of the Pneumococcus. If a small amount of a 

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

 coccic serum, an agglutination of the organisms occurs. The 

 phenomenon 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 pneumo- 

 coccus infection from those due to other bacteria. Whether the 

 method is reliable has still to be proved. It has been shown 

 that a serum which agglutinates the pneumococcus may also 

 agglutinate streptococci isolated from various sources. Such 

 organisms are, however, not so uniformly agglutinated by a 

 pneumococcus serum as are pneumococci isolated from pneu- 

 monic cases. 



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. 106, 109), in the latter case 

 it is usually best not to decolorise 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. 74). (6) Friedlander 's pneumobacillus can 

 be readily isolated either by ordinary gelatin plates or by 

 successive strokes on agar media. 



