202 ACUTE PNEUMONIA. 



these toxines. Their activity is interfered with by an hour's 

 exposure at 60 G, but, as in the case of other toxines, whether 

 they are really proteids, or non-proteid bodies carried down 

 with the latter in the methods of precipitation used, we do 

 not know. 



Immunisation against the Pneumococcus. Animals can 

 be immunised against the pneumococcus either by inocula- 

 tion with attenuated cultures or by the injection of toxic 

 bodies derived from cultures. The former can be effected 

 by cultures which have become attenuated by growth on 

 artificial media, or by the naturally attenuated cocci which 

 occur in the sputum after the crisis of the disease. Netter 

 effected immunisation by injecting an emulsion of the dried 

 spleen of an animal dead of pneumococcus septicaemia. 

 Here the cocci were attenuated by the drying. Immunisa- 

 tion by toxic products has been effected in various ways. 

 The Klemperers found that injection of rusty sputum kept 

 at 60 C. for one to two hours and then filtered, and of toxine 

 similarly treated, had a like result. In all cases one or two 

 injections of the modified bacteria or toxine were sufficient for 

 immunisation. It was three days in the case of intravenous 

 injection, and fourteen days in the case of subcutaneous 

 injection, before immunity was established, and the latter 

 lasted a month or more. The immunity was accompanied 

 by the development in the blood of antitoxic substances 

 which had no effect either outside or inside the body in 

 killing the pneumococci, but merely neutralised their toxines. 

 Such antitoxines not only protected a rabbit against sub- 

 sequent inoculation with pneumococci, but if injected within 

 twenty-four hours after inoculation, prevented death. 



The interpretation of these immunisation experiments is 

 difficult. Isaeff has denied that antitoxic properties exist 

 in the serum of immunised animals, but in the absence 

 of any attempts to standardise the pneumotoxin, his ex- 

 periments must be received with caution, as the amount of 

 serum used might be quite insufficient to neutralise the 

 amount of toxine, and yet it might possess antitoxic pro- 

 perties. Others have held in opposition to the Klemperers 



