346 PATHOGENIC MICROORGANISMS 



antihemolytic substances. 1 They exert, however, demonstrable bacteri- 

 cidal power both in vivo and in vitro and distinctly enhance phagocytosis 

 when brought into contact with leucocytes and streptococci. This 

 "opsonic" power has been noticed both intraperitoneally 2 and in vitro. 3 



The protective value of streptococcus immune sera for infected 

 animals is considerable, reaching often a potency hardly explicable by 

 the demonstrable bactericidal or opsonic power, and thereby suggesting 

 some other active factor not understood as yet. 4 Aronson 6 has produced 

 immune sera by the treatment of horses with a streptococcus derived 

 from a ease of scarlatina, 0.0004 c.c. of which sufficed to protect mice 

 from ten times the fatal dose of a streptococcus culture. These high 

 protective values, however, are obtained only when the serum injections 

 are given simultaneously with the bacteria. Given four or six hours 

 after infection, much higher dosage must be employed and protective 

 results are much less regular in occurrence. 6 Other antistreptococcic 

 sera have been produced by Denys, Menger, Tavel, and others, all show- 

 ing more or less marked potency in protecting animals. 7 



Since these sera, while in a general way potent against all streptococci, 

 have been found protective chiefly against the specific microorganism em- 

 ployed for their production, Van de Velde, 8 Denys, Aronson, and others 

 have advised the immunization of the animal with a large variety of 

 streptococcus races, derived from many different human sources. The 

 resulting " polyvalent" serum is more apt to exert equally high protective 

 powers against all streptococcus infections. The therapeutic value of 

 such sera in the treatment of human infections is still sub judice. Un- 

 deniably favorable reports are published each year in increasing number, 

 but are by no means regular or comparable to the results obtained in 

 diphtheria with diphtheria antitoxin. Nevertheless, in mild cases or in 

 those in which the lesions have been distinctly localized, the sera seemed 

 to be sufficiently useful to justify their use and necessitate their stand- 

 ardization. 



1 Lingelsheim, Zeit. f. Hyg., x, 1891. 2 Bordet, Ann. de 1'Inst. Pasteur, 1897. 



3 Denys et Leclef, Cellule, t. ix. 



4 Denys et Marchand, "Mecanisme de I'lmmunite"," etc., Brussels, 1896. 



6 Aronson, Berl. klin. Woch., xxxii, 1896; ibid., xb'i and xliii, 1902; ibid., viii and 

 ix, 1905. 



6 Denys, "Le Se"rum antistreptoc.," Louvain, 1896; Van de Velde, Ann. de 1'Inst. 

 Pasteur, 1896. 



7 Denys et Marchand, Bull, de 1'acad. roy. de med. de Belgique, 1898; Menger, 

 Berl. klin. Woch., 1902; Tavel, Corr.-Bl. f. Schw. Aerzte. 



8 Van de Velde, Arch, de me"d. exp6r., 1897. 



