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 



