432 INFLUENZA. 



the optimum temperature being that of the body. The influenza 

 bacillus is a strictly aerobic organism. 



The powers of resistance of this organism are of a low order. 

 Pfeiffer found that dried cultures kept at the ordinary tempera- 

 ture were usually dead in twenty hours, and that if sputum were 

 kept in a dry condition for two days, all the influenza bacilK 

 were dead, or rather cultures could be no longer obtained. 

 Their duration of life in ordinary water is also short, the bacilli 

 usually being dead within two days. From these experiments 

 Pfeiffer concludes that outside the body in ordinary conditions 

 they cannot multiply, and can remain alive only for a short time. 

 The mode of infection in the disease he accordingly considers 

 to be chiefly by means of mucus, etc. 



Distribution in the Body. — The bacilli are found chiefly in 

 the respiratory passages in influenza. They may be present in 

 large numbers in the nasal secretion-, generally mixed with a 

 considerable number of other organisms, but it is in the small 

 masses of greenish-yellow sputum from the bronchi that they 

 occur in largest numbers, and in many cases almost in a state of 

 purity. They occur in clumps which may contain as many as 

 lOO bacilli, and in the early stages of the disease are chiefly lying 

 free. As the disease advances, they may be found in consider- 

 able numbers within the leucocytes, and towards the end of the 

 disease a large proportion have this position. It is a matter of 

 considerable importance, however, that they may persist for 

 weeks after symptoms of the disease have disappeared, and may 

 still be detected in the sputum. Especially is this the case when 

 there is any chronic pulmonary disease. They also occur in 

 large numbers in the capillary bronchitis and catarrhal pneu- 

 monia of influenza, as Pfeiffer showed by means of sections of 

 the affected parts. In these sections he found the bacilli lying 

 amongst the leucocytes which filled the minute bronchi, and 

 also penetrating between the epithelial cells and into the super- 

 ficial parts of the mucous membrane. Their presence sets up a 

 marked leucocytic emigration in the peribronchial tissue, the 

 leucocytes passing in large numbers into the lumen of the tubes 

 and sometimes taking up the bacilli. Other organisms also, 

 especially Fraenkel's pneumococcus, may be concerned in the 

 pneumonic conditions following influenza. 



In some cases influenza occurs in tubercular subjects, or is 



