258 PASSIVE IMMUNIZATION 



of other non-antitoxic sera, viz., by starting the immunization with 

 small doses of killed-off cultures and progressively increasing the 

 dose, until finally full virulent living organisms are injected. At the 

 Serum Institute of Vienna, bouillon cultures of from two to eight 

 days' growth are used, the initial dose being 0.5 c.c., and the final 

 one varying between 100 and 200 c.c., all the injections being given 

 subcutaneously. The animals are not bled until the immunization 

 has been continued for about six months. The serum is then tested 

 in reference to its bacteriological purity and titer, and finally put up 

 in doses of 50 and 100 c.c. each, without any preservative. 



In making up the polyvalent antigen for immunization, it is con- 

 venient, even though all the other strains be of human origin and 

 not passed through animals, to introduce one strain which has been 

 so treated and brought to a high degree of virulence, for mice, for 

 example, so as to have an approximative indicator at least for the 

 potency of the antiserum, this being then standardized against that 

 particular " animalized" strain. At the same institute that dose 

 of streptococci which will kill a white mouse at the expiration of or 

 just preceding the end of four days is designated as a single lethal 

 dose; but in testing an antiserum, ten times this amount is chosen 

 as the dose against which one unit of antiserum should afford pro- 

 tection. A simple normal serum is one of which 0.01 c.c. will afford 

 this degree of protection, and 1 c.c. of such a serum is said to con- 

 tain a single immunization unit, and 1 c.c. will accordingly protect 

 1000 mice against a single lethal dose each. The Vienna serum, as 

 it is now marketed, contains 20 to 40 units to the cubic centim- 

 eter. 



Dosage and Usage. Prophylactic Doses. For prophylactic pur- 

 poses, antistreptococcus serum has been recommended in connection 

 with scarlatina and the puerperal process, either by itself or in com- 

 bination with the use of a vaccine. To prepare the latter, F. Meyer 

 suggests that a bouillon culture of a corresponding strain be obtained, 

 centrifugalized, the sediment washed repeatedly with saline, and 

 finally emulsified with a quantity of 0.5 per cent, carbolic acid in 

 saline, equal to the volume of the initial culture. The resultant 

 emulsion is killed off by heating for six hours at a temperature of 

 65 C., when it is tested bacteriologically and shaken overnight in a 

 shaking machine. This constitutes the finished vaccine, which does 

 not need to be counted out. The individual in question receives a 



