CAUSING ACUTE INFECTIONS. 75 



blood is present on the media. Heat kills the bacillus 

 readily; an exposure for a few minutes at 60 C. is 

 sufficient. Drying also kills it quickly. 



The infection manifests itself chiefly in the nose, 

 throat, and bronchi, but may extend to the lungs and 

 give rise to pneumonia. From the nose the infection 

 often extends to involve the accessory sinuses and the 

 middle ear. Exceptionally the infection may extend 

 to the meninges. During the winter of 1912 the 

 writer found the influenza bacilli in the circulating 

 blood of a case of septic endocarditis. The incubation 

 period is from twenty-four to seventy-two hours and 

 the onset is sudden. The bacilli are present in the nose 

 and throat; so to prevent the spread to others these 

 secretions must be collected and destroyed. The 

 bacilli remain in the secretions of the nose, throat, and 

 bronchi for long periods after the acute infection has 

 subsided; in fact, it is probably present all the time 

 in the secretions of some -people. Sporadic cases may 

 be explained by this assumption. 



The immunity following influenza is of very short 

 duration, and reinfection is -very common. Artificial 

 immunity has been attempted by injecting the killed 

 bacilli, but has not proved to be very successful. 



THE BACILLUS OF WHOOPING-COUGH. 



The bacillus causing whooping-cough was de- 

 scribed first by two French bacteriologists, Bordet and 

 Gengou, in 1900. It is small in size, much like the 



