INFLUENZA. 297 



leucocytes blue, and the bacillus is also stained blue, appear- 

 ing as a short, thick rod ; or dumb-bell. 



Desiccation is rapidly fatal ; also a five minutes' exposure to 

 a temperature of 60 C. 



Bacillus influenzse develops rapidly at the body temperature, 

 but best at a temperature slightly lower than this. It is 

 strongly aerobic, and will not grow in the total absence of oxy- 

 gen. It does not form any growth on ordinary media, but 

 develops luxuriantly on blood-serum or on any medium the sur- 

 face of which has been smeared with blood, haemoglobin, or leu- 

 cocytes. It is easily obtained from the sputum or nasal mucus, 

 and also from the throat of persons suffering with influenza. 



On media appropriate for its development very small pearly 

 colonies appear within forty-eight hours. They are shining, 

 moist and transparent, and may easily escape notice at first. 

 They frequently have the appearance of a small opalescent 

 drop of water. Old colonies turn yellowish brown. The 

 colonies rarely become confluent. 



Pathogenesis : The influenza bacillus is apparently patho- 

 genic for man only, as it has so far been impossible to pro- 

 duce the typical disease in animals by inoculation. When 

 inoculated with a large quantity of the culture animals die 

 with symptoms of intense intoxication. 



In man infection probably takes place through the air- 

 passages, in which the previous condition of the lining mucosa 

 is of importance. The bacillus cannot withstand desiccation, 

 but when contained in a plug of mucus it remains alive for a 

 considerable period of time. The secretions from the mucous 

 membranes are the means of spreading the disease. Cough- 

 ing or sneezing forces the infected mucus out of the patient's 

 nose or throat, and the disease is thus conveyed directly to 

 other individuals. 



It has been suggested that air-currents carry the disease for 

 miles from the original seat of the disease. Severe epidemics 

 of the disease, separated perhaps hundreds of miles, have 

 been accounted for in this way. The probability is, however, 

 that if the origin of such epidemics is carefully looked into, 

 it will be found that some individual who is convalescent 

 from influenza was really the carrier of the disease. 



