118 THE ACUTE SELF-LIMITED INFECTIONS 



tissue proper. It is comparable in development to the 

 pneumonia caused by the pneumococcus. The bacillus may 

 at times form pus. 



A very important and highly fatal form of influenzal 

 infection is meningitis due to a blood distribution of the 

 organisms in cases of pneumonia or other local lesion, but at 

 times arising without previous history of illness. The disease 

 is clinically similar to epidemic meningitis and the fluid in the 

 meningeal spaces is likewise purulent. 



The attack of influenza runs an acute course. It leaves 

 but a transient immunity, and one attack is said actually 

 to predispose to another when the individual is exposed 

 subsequently. As complications of influenza of the upper air 

 passages we may have pus in the sinuses about the nose, or 

 otitis media. 



While influenza is an acute disease and the bacteria are 

 actively virulent during an attack, it is believed that they 

 remain in the upper air passages in abeyance and not produc- 

 ing disease for long periods after the acute symptoms have 

 subsided. When they are received in sputum particles upon 

 the nose or mouth of another person not resistant to them, 

 they regain their activity and inflame the parts. It is said 

 that they may remain in the lung tissue for a long time until 

 some reduction of the person's resistance permits the light- 

 ing up of a pneumonia. 



With these facts in mind it is not difficult to understand 

 how sporadic cases occur and how the disease spreads rapidly 

 from one patient to another. The bacilli get to work on the 

 mucous membranes rapidly, and the incubation period is 

 short, three days at the longest. Epidemics have been known 

 to spread over whole continents in a season. Many observers 

 believe that other organisms, notably streptococci, help in the 

 production of these acute influenzal colds. It is undoubtedly 

 true that the influenza bacillus is seldom found in pure culture, 

 that is, in absence of some other organism with pathogenic 

 properties. The bacilli are found in the excretions and 



