STUDIES ON THE SERUM OF VACCINATED ANIMALS. 67 



In the tables that follow the + sign indicates that the granular 

 transformation took place. Now that we have considered the 

 technique certain points may be considered. 



First. Does the method of observation indicated show delicate 

 differences in bactericidal power between two fluids? 



It is already known that normal serum alone will sometimes pro- 

 duce a partial transformation of the vibrio, but this effect is relatively 

 slight. We also know that the injection of normal serum or even 

 bouillon into the peritoneal cavity of a normal guinea-pig increases 

 within certain limits the non-specific bactericidal property of this 

 guinea-pig's serum. This increase in bactericidal property may be 

 detected by our method. A small amount of blood is taken from 

 a guinea-pig; the animal is then given 4 c.c. of normal guinea-pig 

 serum and 24 hours later a new specimen of blood is taken. The 

 effect of these two sera on the cholera vibrio without the addition 

 of cholera serum is then determined. A relatively weak culture is 

 used. Since no preventive serum is used the transformation of the 

 vibrios with either of these sera is only partial. It may, however, 

 be noted that the serum obtained from the animal after injection 

 of normal serum causes metamorphosis in many more vibrios than 

 does the serum obtained before injection; there are also many more 

 non-motile vibrios. The difference between the two preparations 

 is very distinct and demonstrates the delicacy of this method. We 

 repeat that the phenomena, although relatively different in degree, 

 are only partial in both instances and incomplete unless a drop of 

 preventive serum is added. 



Second. Is the bactericidal substance of normal serum still present 

 in the blood of animals that have succumbed to certain infections or 

 intoxications? Is it also present in the animals that have been immu- 

 nized against organisms other than the cholera vibrio? 



The blood of a guinea-pig that had died of anthrax, the blood of 

 a rabbit that had just succumbed to a pneumococcus infection, the 

 pleural exudate of a guinea-pig that had died of diphtheria toxin, 

 and the blood of a guinea-pig that had been vaccinated against 

 cholera and had died of cholera toxin, all gave Pfeiffer's phenomenon 

 in the presence of cholera serum. The blood of the last animal, in 

 spite of the fatal intoxication, brought about Pfeiffer's transfor- 

 mation without the addition of cholera serum, that is, the blood 



