BIOCHEMICAL FEATURES 99 



by repeatedly freezing and thawing pneumococci was followed by 

 marked hemorrhagic lesions on all or a part of the external sur- 

 face that was free from hair, and at necropsy hemorrhagic areas 

 could be found in practically every tissue of the mouse. The adju- 

 vant action of the extract was seen when mice, dying after injec- 

 tion with extract followed several hours later by culture inocula- 

 tion, developed more marked hemorrhagic lesions than any other 

 group of mice studied. Fresh filtrates of virulent pneumococci pro- 

 duced slight pathological reactions in mice but, when the filtrates 

 were injected with a culture of low virulence, 71 per cent of the 

 mice at necropsy showed a fibrino-purulent pleuritis. The results 

 might be interpreted as pointing to the production of an aggres- 

 sin-like substance in the early stages of pneumococcal growth with 

 the development of a more violent poison as growth continues and 

 the cells undergo autolysis. 



Jamieson and Powell 676 also described a skin-reacting substance 

 in pneumococci. To them its properties were comparable to those 

 of the toxins of some streptococci. The alleged success in develop- 

 ing a neutralizing antiserum led the authors to believe that the 

 present type of antibacterial immune serum would be more valu- 

 able if it contained these antiskin-toxic elements. Sabin (1931), 1203 

 investigating the part anaerobic autolysates of Pneumococcus 

 play in the course of natural infection, came to conclusions dia- 

 metrically opposed to those of Parker and the other students shar- 

 ing her ideas. Sabin wrote: "The only conclusion that may be 

 drawn, however, is that the anaerobically produced toxins prob- 

 ably do not play any part in the causation of death of mice in- 

 fected with very large doses of pneumococci." The failure of "anti- 

 pneumotoxic" serum to modify the course of pneumococcal infec- 

 tion led Sabin to conclude that: "It seems fair to assume that the 

 anaerobically produced toxins are probably products primarily of 

 the enzymatic changes occurring in in vitro autolysis, and play no 

 part in natural infections." The idea of producing an immune se- 

 rum capable of neutralizing the poisonous principles of Pneumo- 



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