92 BIOLOGY OF PNEUMOCOCCUS 



tures of Pneumococcus a toxin was produced that, as demonstrated 

 by the Neisser and Wechsberg method, destroyed leucocytes. Leu- 

 cocidin was present in aerobic and anaerobic cultures of both viru- 

 lent and avirulent strains of Types I, II, and III. It was easily 

 oxidized, but was not injured by exposure to 70° for one hour. The 

 toxin in the preparation was not destroyed by evaporation in a 

 vacuum at 5°, and its action could be enhanced three to four 

 times by the addition to the culture of laked red blood cells. Ap- 

 parently the same cultural conditions governed the production and 

 preservation of both the hemotoxin and leucocidin, although the 

 latter was distinguishable by its greater thermostability and its 

 appearance in cultures where no hemotoxin could be demonstrated. 

 The filtrates containing active leucocidin were not toxic for mice in 

 two cubic centimeter amounts injected intraperitoneally, and re- 

 peated doses of the filtrate gave only slight protection. Simultane- 

 ous injections of the extract and avirulent pneumococci did not 

 raise the virulence of the strain, so that the leucocidin does not 

 share this alleged action of the so-called virulin. Sterile superna- 

 tant fluids of phenolized exudates of rabbits with empyema, while 

 in themselves not toxic, upon repeated intravenous injection pro- 

 duced an antileucocidin. Normal rabbit serum did not neutralize 

 the pneumococcal leucocidin, whereas the majority of human se- 

 rums tested possessed neutralizing properties. 



One more morbid effect elicited by pneumococcal extracts or 

 autolysates deserves attention and that is the necrotizing principle 

 reported by Parker. 1059 " 60 This principle is a filtrable substance, is 

 extremely thermolabile, is sensitive to oxidation, and can be sepa- 

 rated from hemotoxin by adsorption with red blood cells, since the 

 necrosis-producing principle remains unaffected after removal of 

 the hemotoxin. The necrotizing substance or substances obtained 

 from both Types I and II pneumococci are neutralized by Type I 

 antipneumococcic serum, and hence the necrotizing substance is 

 not type-specific. 



The virulin, leucocidin, and, to coin a name, the necrotin have 



