STAPHYLOCOCCUS PYOGENES AUREUS 329 



staphylococci growing upon blood-agar plate cultures. Neisser and 

 Wechsberg ' then showed that this hemolytic substance, secreted by the 

 staphylococcus, could be demonstrated in filtrates of bouillon cultures. 

 Such hemolysins are produced by Staphylococcus aureus, and, to a 

 lesser degree, by Staphylococcus albus. The quantity produced varies 

 enormously with different strains and seems to be roughly proportionate 

 to the virulence of the particular microorganism, though exceptions to 

 this rule are not uncommon. Absolutely avirulent races do not, so 

 far as we know, produce hemolysins. The culture medium most favor- 

 able to the formation of these substances is, according to Neisser and 

 Wechsberg, a moderately alkaline beef bouillon. Cultivated at 37.5° C, 

 the bouillon contains the maximimi amount of hemolytic substance be- 

 tween the eighth and fourteenth day, and this may be separated from 

 the bacteria by filtration through Berkefeld or Chamberland filters. 



The hemolytic action may be observed by the general technique for 

 determining hemolysis (given on page 259) . It is important to wash 

 the red blood corpuscles used for the experiments, since many animals 

 normally possess smaU quantities of antihemolysin in their blood-sera 

 (man and horse especially) .^ The red blood corpuscles of rabbits, dogs, 

 and guinea-pigs are extremely susceptible to the action of the staphylo- 

 hemolysin. Those of man are less easily injured by it. The hemolytic 

 action takes place, as Todd* and others * have shown, not only in 

 vitro, but in the living animal as well. 



The staphylo-hemolysin is comparatively thermolabile. According 

 to Neisser and Wechsberg, heating it to 56° C. for twenty minutes de- 

 stroys it. According to some other authors, however, higher tempera- 

 tures (60° to 80° C.) are required. Reactivation of a destroyed staphylo- 

 hemolysin has so far been unsuccessful. The fact that antistaphylolysin 

 is occasionally present in normal sera has been mentioned above. This 

 antibody is most abundant in the blood of horses and of man. Arti- 

 ficially antistaphylolysin formation is easily induced by subcutaneous 

 inoculation of staphylolysin into rabbits. 



Leucocidin. — In 1894, Van de Velde ^ discovered that the pleural 

 exudate of rabbits following the injection of virulent staphylococci 

 showed marked evidences of leucocyte destruction. He was subse- 



' Neisser und Wechsberg, Zeit. f. Hyg., xxxvi, 190L 



2 Neisser, Deut. med. Woch., 1900. 



3 Todd, Trans. London Path. Soc, 1902. 

 'Kraus, Wien. klin. Woch., 1902. 



5 Van de Velde, La Cellule, x, 1894. 



