INFLUENZA BACILLUS. 327 
the air-passages; the general symptoms produced are 
due probably to the absorption of the toxic products of 
the specific organism, these poisons being particularly 
active in their effects on the central nervous system. 
The discovery of this bacillus enables us to explain 
many things, previously unaccountable, in the cause of 
epidemic influenza. We now know, from the prop- 
erty of the influenza bacillus not being able to exist for 
long periods in dust, that the disease is not transmis- 
sible to great distances through the air. We also 
know that the infective material is contained only in 
the catarrhal secretions. Sporadic cases, or the sudden 
eruption of epidemics in any localities from which the 
disease has been absent for a long time, or where there 
has been no new importation of infection, may possibly 
_be explained by the fact that the bacilli, as already 
mentioned, often remain latent in the lungs or bronchial 
secretions of the body for many months, and perhaps 
years, and then become active again, when under favor- 
able circumstances they may be communicated to others. 
The bacteriological diagnosis of influenza is of consider- 
able importance for the identification of clinically doubt- 
ful cases, which, from their clinical symptoms, may be 
mistaken for grippe, or vice versa, such as bronchitis, 
pneumonia, or tuberculosis. Up to the present time, 
however, the diagnosis gives us little help in prognosis 
or treatment. 
In acute uncomplicated cases the probable diagnosis 
can be frequently made by microscopical examinations 
of stained preparations of the sputum, there being pres- 
ent enormous numbers of small bacilli. In chronic cases 
or those of mixed infection the culture method usually 
gives a positive result. The bacillus of influenza is so 
