38 VACCINE AND SEKUM THERAPY 



no serious symptoms. Slightly larger doses give rise 

 to definite symptoms of cholera poisoning. These 

 symptoms of poisoning gradually disappear, and after 

 twenty-four hours the guinea-pigs are again normal. 

 If the quantity of cholera culture is carefully increased 

 up to the minimal lethal dose, the animal dies with 

 all the typical symptoms of cholera intoxication, but 

 on autopsy the peritoneum is found to be perfectly 

 sterile. Finally, if larger quantities of living cholera 

 spirilla are injected, the peritoneal cavity shows a 

 profuse, serous, and sometimes a hemorrhagic 

 exudate, which contains innumerable active micro- 

 organisms. 



This experiment demonstrates the fact that the 

 normal guinea-pigs which receive enough of the 

 cholera vibrios to prove fatal have destroyed the vibrios 

 and presumably died from the poisons thus liberated, 

 and not from the poisons secreted by the living 

 vibrios. It is only when the animal's system is 

 previously flooded with an overwhelming dose that 

 the vibrios are found alive and multiplying even 

 locally in the peritoneum after death. This does not 

 prove, however, that no multiplication goes on hand 

 in hand with the destruction of germs in the infected 

 animal ; on the contrary, such a multiplication is 

 rather the rule than the exception. This has been 

 well illustrated by the experiments of Pfeiffer and 

 Wassermann, who, after having shown that the blood 

 serum of humans who have recovered from Asiatic 

 cholera has the power to protect guinea-pigs from 



