64 STUDIES IN IMMUNITY. 



organic substances than usual. And, what is more, it has by no 

 means been proved that organisms that differ slightly from Koch's 

 organisms are incapable of producing cholera. For example, 

 the vibrio of Massaouah, which is unlike the cholera organisms 

 usually met with, is unquestionably a cause of cholera. (Fermi's 

 experiment.) This organism, however, does not fulfill Pfeiffer's 

 condition. 



Nevertheless, since the majority of cholera vibrios recovered 

 from the stools of cholera cases give the phenomenon, the method 

 may be recommended, with a certain reserve as to negative results. 



IV. PFEIFFER'S PHENOMENON WITH THE VIBRIO 

 METCHNIKOVI. 



Will all vibrios, even the most virulent of them, undergo trans- 

 formation outside the protoplasm of leucocytes when injected into 

 the peritoneal cavity of specifically immunized guinea-pigs? Is 

 the vibrio Metchnikovi, the virulence of which is recognized, 

 easily altered by the peritoneal fluid? 



We injected ^ of a 24-hour agar culture of vibrio Metchnikovi 

 into a guinea-pig immunized by repeated injections of killed or 

 living cultures. The serum of this animal was highly preventive. 

 The organisms were rapidly clumped, but very few of them were 

 morphologically changed. After an hour, for example, in addition 

 to the majority of intact vibrios, a few individuals were found in 

 these clumps broken up into fine granulations and others that 

 stained poorly, but were morphologically intact. The typical 

 transformation into large granulations was only to be found in 

 the protoplasm of polynuclear leucocytes which contained intact 

 vibrios as well. One or two hours after injection the leucocytes 

 were found clumped together. Later they increased in number and 

 many were seen scattered throughout the fluid; 6 hours after 

 injection the number of leucocytes was relatively large and the 

 vibrios were few. In a preparation from the exudate 6 hours 

 and 20 minutes after injection an unphagocyted and morpho- 

 logically intact clump of vibrios was, however, noted. It is 

 evident, then, that not all vibrios undergo granular transformation 

 equally well. 



