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tion io haemoglobin, microscopic morphology, tendency to die 

 out easily). 



Although these bacteria are called „haemolytic, haemoglo- 

 binophilic bacteria" the latter adjective is not quite correct, 

 especially because we ought certainly to include in this group 

 strains which can grow quite well without haemoglobin. The 

 reason for keeping the term nevertheless, is partly because 

 the majority of the strains must be termed haemoglobinophilic, 

 and partly because the group is identical with that described 

 by other authors in a similar manner. 



2. Bordet's Whboping=Cough Bacillus. 



Although the bacillus described by Bordet & Gengou in 

 1906 as the organism of whooping-cough, ought to be regarded, 

 on the basis of their discovery and the work of later investiga- 

 tors (which will not be reviewed here), as a well defined 

 bacterial species distinct from Pfeiffer's bacillus, it appears 

 from comments made by Belfanti, Andrewes, and Rivers 

 (1) that this conception is still far from being generally held. 

 I have therefore thought it not superfluous to subject this 

 question to a fresh investigation on a large scale. 



The extensive material relating to the whooping-cough ba- 

 cillus which the diagnostic investigations of the State Serum 

 Institute started at the instigation of Meyer & Chievitz's (1—5) 

 work, has constantly placed at my disposal, made it easy to 

 examine a large number of strains of this bacillus from various 

 points of view and thus obtain a solid basis for a comparison 

 between it and Pfeiffer's bacillus. It should first of all be 

 remarked that the investigation of these whooping-cough ba- 

 cillus strains has not produced anything really new with regard 

 to this organism, but on account of the large number of strains 

 examined it has further established its characteristic qualities 

 and the by no means few points where it is markedly different 

 from the whole group of Pfeiffer's bacilli. 



The differences between the two species of bacteria upon 

 which most stress has hitherto been laid, are the serological 

 ones. From -the investigations of Odaira, Inaba, Shiga, Emai, 

 & Egvchi, Winholt, Olmstead & Povitzky and others it 



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