ANTISTRKPTOCOCCUS SERUM. 283 



cases of scarlet fever is believed by Moser and others 

 to be peculiar to that disease, and consequently the anti- 

 streptococcus serum obtained by immunization with such 

 an organism is believed to possess little curative pro- 

 perties against infections caused by other strains of 

 streptococci. If this idea should prove correct then it 

 will be necessary to obtain serum from animals that 

 have been simultaneously immunized with a number of 

 strains of streptococci derived from various disease con- 

 ditions a so-called polyvalent serum. 



Other experimenters believe that the frequent passage 

 of a culture of streptococcus through the lower animals 

 renders it less virulent, or at least alters its virulence 

 for human beings, and that the serum obtained through 

 the immunization of animals with such cultures is less 

 efficacious than when the original virulence of the 

 organisms is maintained by cultivation on suitable 

 media. 



Though all experimental evidence contraindicates the 

 production of soluble toxins in large amounts by the 

 streptococcus when grown in artificial media, Marmorek 

 still believes that by special methods of cultivation the 

 toxin-forming powers can be augmented, and that the 

 immunization of animals with such cultures serves a use- 

 ful purpose in giving the serum of the treated animal a 

 more definite antitoxic power. 



Aronson prepares his antistreptococcus serum by 

 immunizing horses with streptococcus cultures that have 

 been rendered highly virulent by repeated passage 

 through animals. By this means he secures a 20-fold 

 normal serum, a " normal " serum being one of which 

 0.01 c.c. protects a mouse from 100 times the lethal dose 

 of highly virulent streptococci. Besides this the horses 



