CHAPTER XIX. 



INFLUENZA, WHOOPING-COUGH, PLAGUE, 

 MALTA FEVEE. 



Influenza. 



The first accounts of the organism now known as the influenza 

 bacillus were published simultaneously by Pfeitfer, Kitasato, and 

 (Janon, in January 1892. The two first-mentioned observers 

 found it in the bronchial 

 sputum, and obtained pure 

 cultures, and Canon ob- 

 served it in the blood in 

 a few cases of the disease. 

 It is, however, to Pfeiffer's 

 work that we owe most of 

 our knowledge regarding 

 its characters and action. 

 His results have been 

 amply confirmed by those 

 of others in various epi- 

 demics of the disease, and 

 this organism has been 

 generally accepted as the 

 cause of the disease, al- 

 though absolute proof is 

 still wanting. 



Microscopical Charac- 

 ters. — The influenza bacilli as seen in the sputum are very 

 minute rods not exceeding 1 '5 jx in length and '3 /x in thickness. 

 They are straight, with rounded ends, and sometimes stain more 

 deeply at the extremities (Fig. 143). The bacilli occur singly or 

 form clumps by their aggregation, but do not grow into chains. 

 They show no capsule. They take up the basic aniline stains 

 somewhat feebly, and are best stained by a weak solution (1 : 10) 



Flo. 143.— influenza bacilli from a culture 



ou blood-agar. 



Stained with carbol-fuehsin. x 1000. 



