430 PATHOGENIC MICROORGANISMS 



ing to 70 C. This is followed, after ten days, by a second injection 

 of a small quantity of fully virulent cocci. Following this, injections 

 are made at intervals of ten days with constantly increasing doses. 

 Modifications of these general principles arc employed in most 

 laboratories. 



The sera of animals so treated contain no demonstrable antitoxic 

 or antihemolytic substances. 94 It has been claimed that these sera 

 exerted demonstrable bactericidal power both in vitro and in vivo. 

 Personally, we doubt the validity of this claim considerably, since 

 bactericidal action upon Gram-positive cocci by body fluids unaided 

 by leucocytes, is not likely to occur. In all such experiments we 

 believe errors have been made, due to the agglutination of organisms 

 and the subsequent diminution of colonies when the tests were made 

 by plating methods. The opsonic powers of such sera, however, 

 cannot be doubted, and enhancement of phagocytosis has been 

 demonstrated, both in vitro and in vivo. In fact, it was with such 

 sera that Denys made his important observations on the importance 

 of serum in phagocytosis, showing that the immune bodies in the 

 serum acted upon the bacteria and not upon the leucocytes. 



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. 95 Aron- 

 son 96 has produced immune sera by the treatment of horses with a 

 streptococcus derived from a case of scarlatina, 0.0004 c.c. of which 

 sufficed to protect mice from ten times the fatal dose of a strepto- 

 coccus 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. 97 Other antistreptococcic sera have been 

 produced by Denys, Menger, Tavel, and others, all showing more 

 or less marked potency in protecting animals. 98 



94 Lingelsheim, Zeit. f. Hyg., x, 1891. 



95 Denys et Marchand, "Mecanisme de I'immunite, " etc., Brussels, 1896. 



96 Aronson, Berl. klin. Woch., xxxii, 1896; ibid., xlii and xliii, 1902; ibid., viii 

 and ix, 1905. 



97 Denys, "Le Serum antistreptoc., " Louvain, 1896; Van de I'elde, Ann. de 

 Tlnst. Pasteur, 1896. 



w Denys et Marchand, Bull, de 1'acad. roy. de med. de Belgique, :J898; Menger, 

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



