202 



The atypical strains on the whole possess a slighter vita- 

 lity" than the typical, as they die out more easily during 

 repeated subculturing. This is in agreement with the fact men- 

 tioned on p. 127 that in cultures of typical and atypical bacilli 

 of the same age, the latter usually contain far fewer bacilli 

 capable of developing than the former. In accordance with 

 this it is natural to regard the abnormal and pale-stained ele- 

 ments of which the main portion of atypical cultures often 

 consist, as degenerate forms. 



We see therefore that the distinction between „typical" 

 and ^atypical" appears to stand for a fundamental difference, 

 since a relation between this classification and several of the 

 various principal characters of Pfeiffer's bacillus can be de- 

 monstrated. 



The next correlation which interests us is the relation 

 between the occurrence of Pfeiffer's bacillus and its other 

 characters. 



It has been repeatedly stated that in influenza and, perhaps 

 hardly to the same extent, in whooping-cough, the majority 

 of Pfeiffer's bacilli met with are typical, while the atypical 

 are chiefly obtained from normal persons, (and from guinea- 

 pigs). It may be added that the great variations in the occur- 

 rence in healthy persons chiefly — perhaps exclusively — 

 refer to typical Pfeiffer's bacilli. It could not be expected to 

 be otherwise in view of the connection between influenza epi- 

 demics and the distribution among healthy persons. This con- 

 nection has a natural explanation in the fact that the same 

 bacilli which first spread among influenza patients, afterwards 

 extended to healthy individuals, and thus we cannot expect 

 to find characteristic differences between the bacilli from the 

 two different sources. Other explanations are however feasible 

 and it will therefore not be amiss to compare the characters 

 of Pfeiffer's bacillus from influenza, from other diseases, from 

 healthy persons, and from guinea-pigs. Particular attention 

 must be bestowed upon seeking for a difference between Pfeif- 

 fer's bacillus from influenza and whooping-cough. If no such 

 difference can be detected in the material before us there 

 will be still less cause than hitherto to distinguish between 

 Bacillus pertussis Eppendorf and Pfeiffer's bacillus. 



As the difference in the occurrence of the typical and 



