302 PROTEIN POISONS 



has done much, and still he employs the language of his 

 own theory long since discarded by himself. 



Friedberger and Nathan 1 showed that by the action of 

 normal guinea-pigs' serum on normal horse serum, or vice 

 versa, in proper proportions, a poison is set free. The serum 

 that is to serve as substrate is inactivated by being heated 

 to 56, and this is then acted upon by the ferment in the 

 unheated serum. It will be understood that the amount 

 of the substrate must be small. In fact, it was found that 

 the poison is produced when the substrate contained not 

 more than 1 mg. of protein. When guinea-pig serum was 

 used as the ferment, it was found to act best in quantities 

 of about 6 c.c. For instance, when inactivated horse serum 

 in quantities of from 0.01 to 0.0005 c.c. was incubated with 

 6 c.c. of normal guinea-pig serum for eighteen hours, and 

 then 4 c.c. of this injected intravenously into guinea-pigs 

 of about 200 grams, the animal promptly died from anaphyl- 

 actic shock. On the other hand, when guinea-pig serum 

 was used as the substrate and horse serum as the ferment, 

 somewhat larger quantities of each were needed. For 

 instance, with 0.1 c.c. of inactivated guinea-pig serum 

 incubated with 8 c.c. of horse serum for twenty-four hours 

 a fatal amount of the poison was obtained, while with the 

 substrate reduced to 0.01 c.c. no symptoms were induced. 

 Friedberger, in reporting this work, expressed astonishment 

 that from a very small amount of protein, enormous quan- 

 tities of which, in its unbroken state, could be injected 

 into animals without recognizable effect, there could be 

 obtained a potent poison, and still years before we had 

 split up these proteins by chemical means and obtained 

 the same poison. What we had done with chemical agents, 

 Friedberger did with ferments. We claimed ten years ago 

 that we had split the protein molecule along definite lines 

 of cleavage, and that our product was not a mere degre- 

 dation body. This demonstration that ferments split the 

 protein molecule along the same lines is a justification of 

 our claim. 



1 Zeitsch. f. Immunitatsforschung, 1911, ix, 567. 



