PSEUDOINFLUENZA BACILLI 325 



become active again, when under favorable circumstances they may 

 be communicated to others. The bacteriological diagnosis of influ- 

 enza is of considerable importance for the identification of clinically 

 doubtful cases, which, from their symptoms, may be mistaken for 

 grippe, or vice versa. Among these are bronchitis, pneumonia, or 

 tuberculosis. Up to the present time the diagnosis gives us little help 

 in treatment. 



Tn acute uncomplicated cases the probable diagnosis can be frequently 

 made by microscopic examinations of stained preparations of the 

 sputum, there being present enormous numbers of small bacilli, at first 

 largely free and later largely in the pus cells. In chronic cases or those 

 of mixed infection few or many bacilli may be found and the culture 

 method may be necessary to give even a probable diagnosis. The bacil- 

 lus of influenza is not readily separated by its morphological, staining, 

 and cultural peculiarities from other bacteria belonging to the influenza 

 group and at present it is almost impossible to certainly identify it. 



The Pseudoinfluenza Bacillus. This bacillus is culturally very similar 

 to the typical influenza bacillus, but may be distinguished from it by 

 its larger size and tendency to grow out into long threads. It is not 

 certain but that it is a form of the influenza bacillus. 



Whooping-cough Bacillus. In this disease bacilli are regularly found 

 which differ but slightly from the influenza bacilli. They produce, 

 when injected in animals, agglutinins which are specific for them, but 

 not for influenza bacilli. Both bacilli are affected by the same group 

 (Wollstein). The blood o'f those suffering from whooping-cough 

 agglutinates the whooping-cough bacilli but not the influenza bacilli. 

 Further investigation is required to establish whether they are the 

 exciting factor of the disease. The Koch-Weeks bacillus is also very 

 similar to the influenza bacillus. 



Relation of the Clinical Symptoms to the Bacterial Excitant. There is no 

 doubt that other infections are also included under the clinical forms of 

 influenza, and during an epidemic of bronchopneumonias, irregular types 

 of lobar pneumonias, and cases of bronchitis frequently have symptoms 

 so closely alike that the nature of the bacteria active in the case is very 

 frequently different from that supposed by the clinician. Thus in four 

 consecutive autopsies examined by the writer the influenza bacillus was 

 found almost in pure culture in one case believed to be due to the 

 pneumococcus, and entirely absent in two of the three believed to be 

 due to it. Except for these examinations the clinician would be of the 

 opinion that he had clearly diagnosed bacteriologically the cases, 

 while in fact he had been wrong in three of the four. 



The striking symptoms in acute respiratory diseases are frequently 

 more due to the location of the lesions than to the special variety of 

 organisms producing them. In epidemics of influenza there are, of 

 course, many cases which, on account of their characteristic symptoms, 

 can be fairly certainly attributed to the influenza bacilli. Even under 

 these circumstances error may be made, as, for instance, two cases of 

 apparently typical influenza were reported in a household and both 



