70 POISONOUS PROTEINS 



gram of protein in an animal's body may sup- 

 ply enough poison to kill many such animals. 

 There are other interesting things about this 

 protein poison besides its potency. When 

 amounts of it, even smaller than the minimum 

 lethal dose, are incubated with blood serum in 

 vitro, the serum, in itself inert, becomes fatally 

 poisonous. In these studies a curious phenom- 

 enon has been observed. The incubating serum 

 containing the poison may be fatally active at 

 the expiration of a given time, then later wholly 

 without effect, and later still fatally active. 

 This wave of appearing, disappearing, reap- 

 pearing toxicity we have frequently observed. 

 For it, I have not even the shadow of an expla- 

 nation. It may turn out after all that ferments 

 and antiferments are not concerned in these 

 phenomena. I have tried to think of oscillations 

 induced in a colloidal fluid like the blood serum 

 by the presence of the protein poison, but I have 

 not been able to fix such a concept. 



As was first shown by Friedberger bacterial 

 cellular substance incubated with blood serum 

 in vitro renders the serum poisonous. In re- 

 peating these experiments and injecting the se- 

 rum at intervals, at one time it kills with all the 

 violence of anaphylactic shock, then it has no 

 effect, then again it kills. I have tried to time 



