220 INFLAMMATORY AND SUPPURATIVE CONDITIONS. 



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 pneumo- 

 coccus septicaemia. Here the cocci were attenuated by the 

 drying. Virulent cultures killed by heating at 62 C. have also 

 been used, immunisation being here accomplished by the intra- 

 cellular toxins. The Klemperers found that injection of rusty 

 sputum kept at 60 C. for one to two hours and then filtered, 

 and of filtered or unfiltered bouillon cultures similarly treated, 

 had a like result. In all cases one or two injections of the 

 modified bacteria or toxin 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 laste'd a month or more. The im- 

 munity 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 toxins. Such antitoxins not only protected a rabbit against 

 subsequent inoculation with pneumococci, but if injected within 

 twenty-four hours after inoculation, prevented death. A pro- 

 tective serum has also been obtained by Washbourn, who, as 

 already described, has succeeded in obtaining pneumococcus 

 cultures of constant virulence. This observer immunised a pony 

 by using (i) broth cultures killed by one hour's exposure to 60 

 C. ; (2) living agar cultures; (3) living broth cultures. From 

 this animal a serum of high protective power was obtained. It 

 protected susceptible animals against many times an otherwise 

 fatal dose, and it also had a curative action, only, however, when 

 injected very soon after inoculation. To what the protective 

 properties of such sera are due requires further investigation. 

 In this connection an interesting fact observed by Mennes may 

 be noted, namely, that normal leucocytes only become phagocytic 

 towards pneumococci when they are lying in the serum of an 

 animal immunised against this bacterium. 



If in these sera antitoxins are present this may shed new 

 light on what occurs in man in the case of recovery from 

 pneumonia. The view has been advanced that the crisis so 



