76 MODERN BIOLOGIC THERAPEUSIS 



ization. Sterilization is effected by filtering 

 through paper pulp and then through a steril- 

 ized Berkefeld filter. This filter is made of 

 diatomaceous earth a fine porous material 

 which, while it permits the antitoxin in solu- 

 tion to go through slowly, does not allow any 

 bacteria to pass. The solution is then tested 

 for safety and sterility, and confirmatory po- 

 tency tests are made. 



The method gives a concentration of about 

 five times the original potency of the unrefined 

 serum. In practice, it produces fewer symp- 

 toms of serum sickness than whole serum, due 

 partly to the removal of non-antitoxic protein 

 and, doubtless, also to the fact that the heat- 

 ing of the serum during the refining process 

 diminishes the power to produce anaphylactic 

 symptoms. 



