310 BACTERIOLOGY. 



tuberculosis. These affections usually pass under the 

 name pseudo-tuberculosis. 



THE BACILLUS OF INFLUENZA. 



An important historic epidemic disease, on the nature 

 of which much light has been shed through modern 

 methods of investigation, is influenza. Quoting Hirsch : 

 the first trustworthy literary records that we have of 

 this disease date from the early part of the twelfth 

 century. 



Between 1173 and 1874 it made its epidemic or pan- 

 demic appearance on eighty-six different occasions. Its 

 first appearance in this country was in Massachusetts in 

 1627; since that time there have been twenty-two vis- 

 itations of influenza to the United States. The recent 

 epidemic, namely, that of 1 889-' 90, .appears to have 

 originated in Central Asia and to have spread pretty 

 much over the entire civilized world. The occurrence 

 of influenza is always remarkable for the rapidity with 

 which it spreads. 



During the recent pandemic investigations, having 

 for their object the discovery of its cause, were insti- 

 tuted, with the result of demonstrating in the catarrlial 

 secretions from the air-passages a micro-organism that 

 is claimed to stand in causal relation to influenza. 



This organism, a bacillus, bacilliLs influenzae, as it is 

 called, was discovered, isolated, cultivated, and described 

 by R. Pfeiffer. 



It is a very small, slender, non-spore-forming, non- 

 motile, aerobic bacillus, occurring singly and in pairs, 

 joined end to end. It stains with watery solutions of 

 the ordinary basic aniline dyes; somewhat better with 



