60 STUDIES IN IMMUNITY. 



unst an undoubted cholera vibrio. By injecting this serum they 

 produce a passive immunity in guinea-pigs against the cholera 

 vibrio. If a pathogenic vibrio from asuspected case of enteritis is 

 subsequently injected into these immunized animals they do nol 

 succumb if the vibrio is a true cholera organism. If, on the other 

 hand, the animal docs succumb, they conclude that the culture is 

 not the authentic Koch vibrio. 



Pfeiffer* has recently modified and simplified this diagnostic 

 procedure. He inoculates a normal guinea-pig with a bouillon 

 culture of the suspected organism to which a small amount of anti- 

 cholera serum has been added. If the organism in question is a 

 true cholera vibrio, granular transformation takes place. 



Granular transformation is indicative of a bactericidal effect by 

 the surrounding body fluid on the vibrio. This bactericidal power 

 is specific and affects only those vibrios which are identical with 

 the one used to immunize the animal from which the serum is 

 taken. In addition to Pfeiffer, Dunbar has more recently shown 

 by numerous experiments that those organisms which resemble 

 Koch's vibrio culturally may be considered to be true cholera 

 vibrios if they undergo granular degeneration when injected with 

 cholera serum into the peritoneal cavity of a normal guinea-pig. 

 This means of diagnosis does not require much serum, but is costly 

 on account of the animals used and the time consumed if there are 

 a large number of vibrios to examine, or if there is no well-equipped 

 laboratory at hand. It would therefore be very desirable to use 

 for diagnosis the method indicated, which consists essentially in 

 the production of Pfeiffer's phenomenon in vitro by means of the 

 combined action of preventive serum and blood or serum from a 

 normal animal. This method is very easy and economical and 

 requires only small amounts of preventive serum and fresh blood. 

 A few drops of blood obtained by puncture and taken in a capillary 

 tube will give a drop or two of serum which is sufficient to examine 

 several specimens. 



Let us consider first whether the granular transformation in vitro 

 with our serum occurs with vibrios belonging to species other than 

 that of the Koch vibrio as defined by Pfeiffer. 



Each of the vibrios found in the following table w T as placed with 

 * Pfeiffer, Deutsche medicinische Wochenschrift, 1S94. 



