482 INFLUENZA 



generations by growing the xerosis bacillus along with it ; dead 

 cultures of the latter had not the same favouring effect. Allen 

 has also noted that the growth of the influenza bacillus is aided 

 by the concomitant growth of pneumococci and staphylococci. A 

 very small amount of growth takes place in bouillon, but it is 

 more marked when a little fresh blood is added. The growth 

 forms a thin whitish deposit at the bottom of the flask. The 

 limits of growth are from 25 to 42 (1, the optimum tempera- 

 ture 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 

 bacilli 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 fine particles of disseminated 

 sputum, 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 

 are present in largest numbers, 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 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 

 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 

 superficial parts of the mucous membrane. Other organisms 

 also, especially Fraenkel's pneumococcus, may be concerned in 



