BACTERIA IN INFLUENZA. 389 



Biological Characters. An aerobic, non-motile bacillus. Does 

 not grow in nutrient gelatin at the room temperature. Spore forma- 

 tion not observed . Upon the surface of glycerin-agar in the incubat- 

 ing oven very small, transparent, drop-like colonies are developed at 

 the end of twenty-four hours. These can only be recognized by the 

 aid of a lens. " A remarkable point about them is that the colonies 

 always remain separate from each other, and do not, as all other 

 species known to me do, join together and form a continuous row. 

 This feature is so characteristic that the influenza bacilli can be 

 thereby with certainty distinguished from other bacteria" (Kitasato). 

 On 1.5 per cent sugar-agar the colonies appear as extremely small 

 droplets, clear as water, often only recognizable with a lens 

 (Pfeiffer). 



In bouillon a scanty development occurs, and at the end of twen- 

 ty-four hours small, white particles are seen upon the surface, which 

 subsequently sink to the bottom, forming a white, woolly deposit, 

 while the bouillon above remains transparent. This bacillus does 

 not grow at temperatures below 28 C. 



Canon has obtained colonies, resembling those described by Kita- 

 sato, in cultures from the blood of influenza patients. His cultures 

 were made upon glycerin-agar in Petri's dishes. Ten or twelve drops 

 of blood from a puncture made in the finger of the patient, after 

 sterilization of the surface, were allowed to fall upon the agar medium, 

 and this was placed in the incubating oven. As the number of ba- 

 cilli in the blood is small, a considerable quantity is used. The 

 colonies are visible at the end of twenty-four to forty-eight hours. 



The influenza bacillus is quickly destroyed by desiccation ; a 

 pure culture diluted with water and dried is destroyed with cer- 

 tainty in twenty hours ; in dried sputum the vitality is retained 

 somewhat longer, but no growth occurs after forty hours. The 

 thermal death-point is 60 C. with five minutes' exposure (Pfeiffer 

 and Beck). 



Patliogenesis. Pfeiffer infers that this is the specific cause of 

 influenza in man for the following reasons : 



1. They were found in all uncomplicated cases of influenza ex- 

 amined, in the characteristic purulent bronchial secretion, often in 

 absolutely pure cultures. They were frequently situated in the pro- 

 toplasm of the pus corpuscles ; in fatal cases they were found to 

 have penetrated from the bronchial tubes into the peribronchitic tis- 

 sue, and even to the surface of the pleura, where in two cases they 

 were found in pure cultures in the purulent exudation. 



2. They were only found in cases of influenza. Numerous con- 

 trol experiments proved their absence in ordinary bronchial ca 

 tarrh, etc. 



