DISTRIBUTION OF BACILLI. 407 



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 temperature were usually dead in twenty hours, 

 and that if sputum were kept in a dry condition for two 

 days, all the influenza bacilli were dead. 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 direct contact 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 100 bacilli, and 

 in the early stages of the disease are chiefly lying free. As 

 the disease advances, they may be found in considerable 

 numbers within the leucocytes, and a large proportion have 

 this position towards the end of the disease. It is a 

 matter of considerable importance, however, that they may 

 persist for weeks in the bronchi after symptoms of the 

 disease have disappeared, and may be detected in the 

 sputum. They also occur in large numbers in the capil- 

 lary bronchitis and catarrhal pneumonia 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 



