STAPHYLOCOCCUS PYOGENES AUREUS 331 



culture fluids at incubator temperatures. It is distinct from staphylo- 

 hemolysin as shown by differences in thermostability. 



Soon after Van de Velde's discovery of leucocidin, Denys and Van 

 de Velde l produced an antileucocidin by treating rabbits with pleural 

 exudate containing leucocidin. Neisser and Wechsberg 2 later confirmed 

 these results and showed that among staphylococci, leucocidin is not 

 specific, the toxin of all strains of Staphylococcus aureus and albus 

 examined being neutralizable by the same antileucocidin. Antileuco- 

 cidin is often found in the normal sera of horses and man. 3 



Leucocidin should not be confounded with "leucotoxin," a substance 

 obtained in serum by treatment of animals with leucocytes, a true 

 "cytotoxin," having no connection whatever with the staphylococcus. 



Staphylococci, besides the toxic substances already mentioned, give 

 rise to gelatinase, spoken of in the section upon cultivation, and to a 

 proteolytic ferment by means of which albuminous media (Loefner's 

 serum) may be slightly digested. 



Immunization. Animals can be rendered actively immune by re- 

 peated inoculations with carefully graded doses of living or dead staphy- 

 lococcus cultures. 4 The production of antistaphylolysin and of anti- 

 leucocidin in the sera of animals so treated, has been alluded to in the 

 preceding sections. The sera of such actively immunized animals 

 possess distinct protective power when administered to other animals, 

 slightly before or at the same time with an inoculation of staphylo- 

 cocci. They do not, however, exhibit very high bactericidal power in 

 vitro, the protective properties depending probably entirely upon their 

 opsonic contents. 5 



Agglutinins have been demonstrated in staphylococcus immune sera 

 by a number of authors, and have been of some slight value in differ- 

 entiating between the several groups of staphylococci. 6 A rather sur- 

 prising result of these researches has been the recognition that immune 

 sera obtained with pathogenic staphylococci will agglutinate other 

 pathogenic staphylococci, whether belonging to the group of Staphy- 

 lococcus pyogenes aureus or that of Staphylococcus pyogenes albus, 



1 Denys et Van de Velde, La Cellule, xi, 1895. 



2 Loc. cit. 



3 Van de Velde, Presse me'dicale, i, 1900. 



4 Richet et Hericourt, Compt. rend, de 1'acad. des sci., cvii, 1888. 

 6 Kolle uud Otto, Zeit. f. Hyg., xli, 1902. 



6 Proscher, Cent. f. Bakt., xxx;v, 1903; v. lAngelsfwim, "Aetiol u, Therap. <t, 

 Staphyl.," etc., Wien, 1900, 

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