372 BACTERIOLOGY. 



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

 itations of influenza to the United States. The pan- 

 demic of 1889-'90, the most severe for a long time, 

 appears to have originated in Central Asia and to have 

 spread pretty much over the entire civilized world. The 

 advent of influenza in a community is always remark- 

 able for its astonishing rate of transmission from per- 

 son to person and its dissemination over wide areas. 



During the recent pandemic investigations having 

 for their object the discovery of its cause Avere insti- 

 tuted, with the result of demonstrating in the catarrhal 



Fig. 66. 



Bacillus of influenza in sputum. 



secretions from the air-passages a micro-organism that 

 is claimed to stand in causal relation to influenza. 



This organism, baoillus influenzce, as it is called, was 

 discovered, isolated, cultivated, and described by E. 

 Pfeiffer. 



It is a very small, slender, non-spore-foi-ming, non- 



