514 



Journal of Agricultural Research 



Vol. XIX, No. lo 



B. boiulinus filtrate. Good fixations were obtained by using B. hotulinus 

 (type B) filtrate with B. hotulinus (type B) immune serum, but type B 

 filtrate and type A serum would not produce a fixation, nor would type A 

 filtrate produce a fixation with type B serum. Considering that type B 

 immune serum does not protect guinea pigs against type A filtrate, which 

 contains the type A toxin, and vice versa, the absence of fixation when 

 using one type of serum and the other type of filtrate as antigen is quite 

 important from a differential standpoint and also serves to indicate the 

 specificity of the reaction obtainable by this method. 



Table I. — Titration of germ-free blackleg filtrate antigen 



Tube No. 



Serum. 



Posi- 

 tive. « 



Nega- 

 tive. & 



Cc. 



Physio- 

 logical 

 salt 

 solution. 



Cc. 



Antigen.'" 



Cc. 



Comple- 

 ment. 



Cc. 



O 



Hemolytic 

 rabbit se- 

 rum and 

 sheep cor- 

 puscle. <* 



Cc. 



Result, e 



+ 

 + 

 + 

 + 

 + 

 + 

 + 



+ 

 + 

 + 



± 

 + 

 + 

 + 



+ 



o Horse serum hyperimmunized to germ-free blackleg filtrate. 



6 Normal horse serum. 



c Germ-free blackleg filtrate. 



d Hemolytic system employed consisted of a 3 per cent suspension of sheep red cells, 2 J4 units of hemolytic 

 amboceptor, and i.Vi tmits of complement, the latter being titrated against the amboceptor and sheep 

 cells. 



t + indicates complete inhibition of hemolysis; ±, partial inhibition of hemolysis; and — , no inhibition 

 of hemolysis. 



Since a blackleg filtrate produced from a pure culture of Bacillus 

 chauveaui and grown under favorable conditions will possess antigenic 

 value in the quantities shown in the preceding table, if a filtrate were 

 encountered that failed to approximate such a titre then only would it 



