55 



agglutination and by absorption, were very closely related. Roos 

 obtained similar results. These divergent results cannot however 

 invalidate the experience of the numerous other authors which refers 

 to a much larger material and to a great extent was obtained with 

 very elaborate and accurately described technique. The divergent 

 results of the two last-named authors are probably due to the 

 technique employed, but it is not possible to throw any further 

 light upon the question (non-specific serum action? Inhibition of 

 agglutination after „ absorption" as a result of altered milieu?) In 

 this connection it may be stated that Yokoi found that Pfeiffer's 

 bacillus and Meningococcus by complement fixation, and by agglutina- 

 tion combined with absorption, were identical! Such a result must 

 certainly depend upon a defective technique and under such cir- 

 cumstances one can naturally not expect to find mutual differences 

 between strains of Pfeiffer's bacillus. 



It is of great importance to know whether the serological 

 reaction of an individual strain keeps constant for a long while 

 and in changing conditions, or whether it is easily and rapidly 

 transformed. 



Judging from our experience of other kinds of bacteria 

 e. g. Pneumococcus and Meningococcus, the serology, and espe- 

 cially the agglutination of a strain, is one of its most con- 

 stant characters which in the large majority of cases prac- 

 tically does not change either on cultivation for a long period 

 or on passage through animals. We must therefore presume 

 the same holds in the case of Pfeiffer's bacillus, if there are 

 no important facts pointing in the opposite direction. For 

 the technique with which differences in the agglutination of 

 Pfeiffer's bacilli have been demonstrated is just the same as that 

 employed to divide Meningococcus and Pneurnococcus into well- 

 defined types. 



The direct observations that have been made as to the 

 constancy or liability to change of the agglutination reactions 

 of Pfeiffer's bacilli do not on the whole indicate that they would 

 act very differently to other bacteria. 



Bieling & Joseph found that a strain of Pfeiffer's bacillus 

 retained its agglutinability unchanged even after 11 mouse passages. 

 Park, Williams. & Cooper, on investigating many strains, found 

 they did not change their type either on cultivation for a long time 

 or by animal passage. Park & Cooper observed 3 chance labora- 

 tory, infections in man and found in each case that the infecting 

 culture and the bacillus cultivated from the patient were serologi- 



