Identity of Bacillus parabotulinus. 163 



toxin mixtures, made up to a constant volume (3 cc.) with saline 

 were placed in conical glasses, the contents thoroughly mixed, incubated 

 for 1? hours at 37° C, and then injected subcutaneously. 



In other experiments it has been shown that 0,1 cc. of this para- 

 botulinus antitoxin is capable of protecting against at least 50 ra.l.d, 

 of toxin. Even the administration of 100 m.l.d. of toxin, with a 

 similar quantity of antitoxin, was followed by but slight symptoms and 

 ultimate recovery. 



It will be noted that the m.l.d. of Type A. botulinus toxin is very 

 large; this was a very weak toxin, and though this strain has a low 

 degree of toxicity much more powerful products have at times been 

 obtained. The dose selected as the m.l.d. for Type B. botulinus toxia 

 was really less than 1 m.l.d., and this is to be ascribed to the toxicity 

 of this filtrate having diminished somewhat since its potency was de- 

 termined. These factors, however, only serve to make the test more 

 crucial. 



The following conclusions are drawn from the above: — 



(a) That the antitoxins employed, parabotulinus and polyvalent 

 botulinus protect against their homologous toxins. 



(b) That parabotulinus antitoxin fails to protect against either 

 type of botulinus toxin, and conversely a polyyalent botulinus 

 antitoxin fails to protect against parabotulinus toxin. 



(c) That normal guinea pig serum possesses no antitoxic value 

 against parabotulinus toxin. 



(In another experiment it has been shown that normal ox 

 serum affords no protection against botulinus toxin.) 



(d) That, from immunity tests alone, there is sufficient evidence 

 to regard B. paralyotulinus as being distinct from B. hotuUnus^ 



Other tests, though not so comprehensive as that given above, 

 have given the same results. 



Conclusion. 



(1) That B parabotulinus produces a true toxin, i.e., a soluble 

 exotoxin obtainable by filtration, producing symptoms only after a 

 definite period of incubation, and capable of inducing the formation 

 of an antitoxin. 



(2) That though the toxins of B. parabotulinus and of B. botulinus 

 are identical in their action, the antitoxin to the one does not protect 

 against the other, and vice versa. 



(3) Aa it has been shown previously that B. parabotulinus differs 

 from B. botulinus (Types A. and B.), both morphologically and cul- 

 turally, and is now demonstrated by toxin-antitoxin tests to be dis- 

 tinct, the specific identity of B. parabotulinus is claimed. 



