IMMUNISA TION A GAINST PNE UMOCOCCUS. 203 



that the serum of immunised animals is bactericidal, and 

 the whole subject requires further investigation. 



If antitoxines exist, their production may shed new light 

 on what occurs in pneumonia in man. The view has been 

 advanced that the crisis so characteristic of a non-fatal case 

 of the disease occurs when the balance of antitoxine against 

 toxine is in favour of the former. The pneumococci after 

 the crisis, as has been proved both culturally and by in- 

 oculation experiments, are still vital and virulent, though not 

 so virulent as when the fever is at its height. On them 

 directly the antitoxine has no effect, but any toxine now 

 elaborated by them is neutralised, and has no longer either 

 local or general pathogenic effects. 



A fact interesting as corroborating the view that the 

 pneumococcus is really the cause of acute lobar pneumonia, 

 is that the serum of patients who have recovered from 

 pneumonia has in a certain proportion of cases a protective 

 effect against the pneumococcus in rabbits. So far as our 

 knowledge goes, such a protective serum is specific, or in 

 other words, protects only against the organism by the 

 action of which its protective properties have been pro- 

 duced, and therefore it must be against the pneumococcus 

 that the human subject requires protection in pneumonia. 



The Klemperers treated a certain number of cases of 

 human pneumonia by serum derived from immune animals, 

 and with apparently a certain measure of success. These 

 results have been followed up by Washbourn, who immun- 

 ised ponies against the pneumococcus, and found that their 

 serum had protective powers when tested in other animals. 

 It is still doubtful whether such serum is really antitoxic, 

 and further investigation is necessary. 



Methods of Examination. These have been already 

 described, but may be summarised thus : (i) 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. (p. 188), in the latter 

 case without decolorising the ground-work of the preparation. 



(2) By cultures, (a) FraenkeFs pneumococcus. With 



