112 MODERN BIOLOGIC THERAPEUSIS 



counts for many of the failures and adverse 

 criticisms connected with some of the antibac- 

 terial sera. In addition to the above tests, rigid 

 bacteriologic and physiologic tests are em- 

 ployed to establish the safety of each lot of 

 serum. 



Polyvalent It has been demonstrated that 

 different cultures of the same species of bacteria 

 vary widely in their biologic properties. Hence, 

 it is essential in preparing antibacterial sera 

 that the horses be inoculated with a number of 

 different races of the specific bacteria, in order 

 to produce a polyvalent serum which will be ef- 

 ficacious against practically all the races of that 

 type of bacteria likely to be encountered. Polyva- 

 lent means, therefore, that the serum is pre- 

 pared from several cultures of the same species 

 of bacteria obtained from many different 

 sources of the same type of infection. The an- 

 tibacterial sera prepared by our laboratories are 

 all polyvalent sera. 



Antitoxic vs. Antibacterial Sera It may be 

 well here to point out the difference between 

 antitoxic sera and antibacterial sera: (1) An- 

 titoxic sera neutralize the toxins or poisons pro- 

 duced by the diphtheria and tetanus bacilli, and 



