Investigations into the Occurrence of 

 Pfeiffers Bacillus. 



The following account of my own investigations is divided 

 into 4 sections. 



First of all (pp. 72—97) an account is given of the occurrence 

 of Pfeiffer's bacillus in influenza, in other diseases, -in healthy 

 persons, and in animals. It has not been my intention to 

 investigate the factors which determine the distribution of the 

 bacillus, but only to try to describe as accurately as possible 

 the facts relating to its occurrence. With this goal in view 

 the numerical results have been treated statistically as far as 

 the material seemed to be adapted for this purpose. 



In the next section (pp. 98—204) the whole of the material 

 collected which deals with such bacteria as for the present 

 are called Pfeiffers bacilli, is investigated as regards a large 

 number of characters that might be expected to be of impor- 

 tance in the classification of these organisms. Only for about 

 150 strains however is the investigation complete; in the case 

 of the others (about 650 strains) only a small number of cha- 

 racters are dealt with, usually just those few which are regarded 

 as especially characteristic of Pfeiffer's bacillus. The number 

 of strains however which are examined more thoroughly, is 

 so large that it is justifiable to conclude the results obtained 

 in the case of the exhaustively examined strains must apply 

 to the whole material. 



The whole investigation has shown on the one hand that 

 all the strains have so much in common that they naturally 

 fall into the same group (species), and on the other hand it 

 has given a complete picture of the differences which are to 

 be observed in this group. In addition care has been taken 

 to give an account of various technical questions. 



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