Resume. 



1. The occurrence of Pfeiffer's bacillus in influenza pa- 

 tients was investigated during 4 epidemics in the years 1918 

 — 1922. It was found only rarely in the first epidemic, while 

 in the next which was only separated from the first by an ex- 

 tremely short interval, it was found decidedly more frequently 

 (in the sputum in 35o/ of the patients and in 51<y of the 

 autopsies on influenzal pneumonia). A more efficient technique 

 would certainly have yielded a somewhat higher percentage 

 in the case of the sputum. 



Pfeiffer's bacillus must certainly have increased in distri- 

 bution in influenza patients between the 1st. and 2nd. epide- 

 mics. Whether any real change in its occurrence in influenza 

 took place later cannot be decided. 



2. Pfeiffer's bacillus was found in influenza most often 

 in the first couple of days after the beginning of the disease. 



3. In whooping-cough this organism could be de- 

 monstrated still more frequently than in influenza, in the 

 first series in all the 12 patients examined. 



4. In measles il had a similar distribution to that of 

 influenza. 



5. It was found in pure culture in the spinal fluid of 5 

 cases of meningitis. 



6. Pfeiffer's bacillus was met with, widely distributed 

 among healthy persons. The occurrence however was 

 very variable in the different groups investigated ranging from 

 8o/o to lOOo/o. 



7. As a direct consequence of each of the 4 epidemics 

 a marked increase in the distribution of Pfeiffer's bacillus 

 among the population as a whole was observed, followed in 

 the succeeding months by a sharp decrease. 



