366 Chapter XII 



If, in the case of the non-specific action of serums, it were 

 allowable to advance the hypothesis of a direct influence of these 

 fluids on the toxins, it would still be impossible to sustain this view 

 where broth fulfils the antitoxic rdle. This fluid, much simpler in 

 composition than any serum, is an excellent culture medium for 

 micro-organisms and one in which the toxins develop well and can be 

 kept for a fairly long period. There is, therefore, not the slightest 

 ground for assigning to it any direct antitoxic action, on the contrary, 

 everything leads us to regard it as an indirect agent, which acts by 

 stimulating the reaction of the animal organism. Here, then, the 

 case would be quite analogous to that of the action of broth as a 

 protective agent against certain bacterial injections, a subject already 

 discussed in the tenth chapter. In this same category of indirect 

 influences also, must be ranked the example of the antitoxic action 

 of the blood of the crayfish against scorpion venom. I have 

 demonstrated in a series of experiments that the fresh blood of the 

 crayfish has the power to prevent fatal intoxication of mice by 

 scorpion venom. Injected in a dose of from 1 to 1*25 c.c., several 

 minutes or an hour before the injection of the rapidly fatal dose of 

 scorpion venom, the crayfish's blood exerts a very distinct preventive 

 action. It might be supposed from this that the crayfish belongs to 

 the group of animals insusceptible to scorpion venom. This, how- 

 ever, is not the case. The crayfish is very susceptible to this poison 

 [385] and succumbs to a quarter the dose necessary to kill a mouse. The 

 blood of the crayfish is, therefore, completely ineffective as a pro- 

 tective to the crayfish itself, and only exerts its action when introduced 

 into the body of the mouse. It might be concluded that it is only 

 after it has been drawn from the crayfish that the blood acquires its 

 antitoxic power. Experiment contradicts this supposition. Crayfish 

 blood, when injected into another crayfish, in equal or greater amount 

 than is necessary to protect a mouse, is incapable of preventing fatal 

 intoxication by scorpion venom, although, here again, the crayfish 

 received only one-quarter of the dose of venom used for the mice. 



We are, therefore, compelled to believe that the crayfish's blood 

 is antitoxic for the mouse, not in virtue of its djrect neutralising 

 action on the venom, but owing to some indirect influence on the 

 organism of the mouse. It is impossible to define, exactly, the 

 mechanism of this action. We may suppose that the blood of the 

 crayfish contains some substance which, by itself, is insufficient to 

 prevent the intoxication, but which becomes active in the presence of 



