PHAGOCYTOSIS 39 



ordinary fcatal doses of the cholera spirilla, even when 

 used in high dilutions, proved that this protective 

 power is not an antitoxic one, but depends largely, 

 if not entirely, on the ability of the serum to aid 

 in the immediate dissolution of the vibrios. Now, 

 however, if the dose was increased to a much larger 

 amount, not even ten thousand times the original 

 amount of serum would protect the animals against 

 the inoculation. 



Now, let us analyse the above facts and seek an 

 explanation of their phenomena. In Pfeiffer and 

 Wassermann's experiments we have seen that even 

 a small amount of cholera-immune serum, when 

 injected into a guinea-pig, protected that animal from 

 a normally fatal dose of cholera vibrios. But, by the 

 phenomenon of Pfeiffer, we have seen that the 

 antibodies in such an immune serum are to all 

 intents and purposes bactericidal — that is, they cause 

 the dissolution and disintegration of the bacteria, but 

 at the same time that the bacteria are undergoing 

 disintegration their poisonous substances, the endo- 

 toxins, are liberated ; and as it is these endotoxins 

 which produce the toxic symptoms in the animal 

 body, there must be some other factor than the anti- 

 bodies within the animal tissues to overcome the 

 amount of toxins which must be liberated from the 

 injection of ordinarily fatal doses of cholera spirilla 

 in the Pfeiffer and Wassermann experiment. 



We have already seen that the neutralising sub- 

 stance for endotoxins is contained within the leuco- 



