STUDIES ON THE SERUM OF VACCINATED ANIMALS. 39 



pathogenic that there is no necessity for injecting large amounts of 

 the culture into the animals, which might be toxic apart from any 

 increase in organisms that may take place. It frequently happens 

 in using a culture of cholera vibrios of low pathogenic power, but 

 of high toxicity (for example, the culture from Eastern Prussia), 

 that well vaccinated guinea-pigs die on receiving a sub-lethal dose, 

 and die, not of infection, but from intoxication; it is well known, 

 indeed, that protection by means of serum, or active immunization 

 by means of bacteria, does not decrease the sensitivity of the animal 

 to the toxin. It is evident, then, that such cultures should not be 

 used in comparing the preventive value of two fluids. The Mas- 

 saouah vibrio employed kills guinea-pigs in a dose of T V of a 24-hour 

 agar culture intraperitoneally. 



The preventive fluids were injected into the peritoneum 24 hours 

 before the intraperitoneal injection of the culture. The agar 

 culture used for injection was suspended in a definite amount of 

 salt solution (0.6 per cent) and formed a homogeneous emulsion 

 that could be easily measured. 



EXPERIMENT 9. Rabbit "A" had been vaccinated against the 

 Massaouah culture and the blood and edema fluid had been studied 

 in respect to their bactericidal properties. 0.25 of a cubic centi- 

 meter of each liquid was injected into the peritoneal cavity of a 

 guinea-pig. The one receiving the serum weighed 330 grams, the 

 one that received edema fluid, 345 grams. Twenty-fours hours 

 later these two guinea-pigs, as well as a control normal guinea-pig 

 (400 grams), received each T V of a culture. The control died 

 rapidly. The two guinea-pigs that had received protective injec- 

 tions recovered. 



In this experiment both the edema fluid and the serum were shown 

 to contain preventive properties. But it was found by increasing 

 the amount of culture and diminishing slightly the amounts of the 

 preventive fluids injected that the properties are not present in 

 equal amounts in the two fluids. 



EXPERIMENT 10. A guinea-pig weighing 500 grams received 

 0.2 of a cubic centimeter of serum from the vaccinated rabbit. 

 Another guinea-pig (525 grams) received 0.2 of a cubic centimeter 

 of edema fluid. A control guinea-pig (535 grams) received 0.2 of a 

 cubic centimeter of normal rabbit serum. Twenty-five hours later 



