QUALITATIVE BACTERIOLOGICAL ANALYSIS. 



cholera serum with different races of cholera vibrios which had 

 been tested as to their virulence by peritoneal injection into 

 guinea-pigs. He found that a serum prepared from the vibrio 

 with the greatest virulence reacted powerfully with all the races, 

 but a serum prepared from the vibrio with least virulence had 

 a very slight action on the most virulent vibrios. For purposes 

 of diagnosis it is therefore important to work with a sufficiently 

 potent sample of cholera serum. Durham also found that 

 vibrios allied to the cholera vibrio reacted with cholera serum. 

 The Vibrio Ivanoff reacted to the different varieties of cholera 

 serum exactly like a cholera vibrio of medium virulence. Also, 

 the influence of the various kinds of cholera serum upon the 

 race of Vibrio Berolinensis agreed with the results obtained 

 upon the different races of cholera vibrios themselves. The 

 Vibrio Sanarelli also reacted markedly with potent cholera 

 serum. Sera prepared by other vibrios, such as the Massowah, 

 Danubicus, and Elwers, had a slight action on cholera vibrios, 

 but weak dilutions of the serum had very little effect. On the 

 other hand, cholera serum had absolutely no effect on the Vibrio 

 Finkler-Prior. With regard to the relation of the agglutina- 

 tion test to Pfeiffer's reaction, Durham concludes that whatever 

 "specific," or preferably "specialised," action a serum has upon 

 a given vibrio, such action has already taken place before the 

 injection is made. The reaction of Pfeiffer's is to be regarded as 

 consisting of two parts : the one being a weakening of the 

 microbes before injection by direct action of the active serum ; 

 the other being the normal bactericidal influence of the guinea- 

 pig^s peritoneal fluid upon these weakened microbes. 



It is thus evident that the serum reactions cannot be considered 

 absolutely diagnostic. Positive reactions, however, especially when 

 obtained with a highly dilute serum, are undoubtedly very strong 

 evidence in favour of the microbe being the true cholera spirillum. 



The cultural reactions are also open to serious criticism. 

 The appearance of the colonies in gelatine-plate cultures has 

 been considered highly characteristic of the cholera spirillum,, 

 and special stress has been laid upon the irregular margin 

 of the young colonies, the margin of the young colonies of 

 most foreign vibrios being quite regular and forming an 

 unbroken circle. Metchnikoff has, however, isolated vibrios 



