CHAPTER XVI. 



INFLUENZA. 

 BACILLUS INFLUENZA (R. PFEIFFER). 



General Characteristics. A minute, non-motile, non-flagellated, 

 non-sporogenous, non-liquefying, non-chromogenic, aerobic, pathogenic 

 bacillus, staining by the ordinary methods, b.ut not by Gram's method, 

 and susceptible of artificial cultivation, chiefly through the addition 

 of hemoglobin to the culture-media. 



Notwithstanding the number of examinations conducted 

 to determine the cause of influenza, it was not until 1892, 

 after the great epidemic, that Pfeiffer* found, in the blood 

 and purulent bronchial discharges, a bacillus that con- 

 formed, in large part, to the requirements of specificity. 



Morphology. The bacilli are very small, having about 

 the same diameter as the bacillus of mouse septicemia, but 

 only half its length (0.2 by 0.5 fi). They are usually soli- 

 tary, but may be united in chains of three or four. 



They are non-motile, have no flagella, and, so far as is 

 known, do not form spores. 



Staining. They stain rather poorly except with such 

 concentrated and penetrating stains as carbol-fuchsin and 

 Loffler's alkaline methylene-blue, and even with these more 

 deeply at the ends than in the middle, so that they appear 

 not a little like diplococci. They do not stain by Gram's 

 method. 



Canon f recommends a rather complicated method for the 

 demonstration of the bacilli in the blood. The blood is 

 spread upon clean cover-glasses in the usual way, thoroughly 

 dried, and then fixed by immersion in absolute alcohol for 

 five minutes. The best stain is Czenzynke's: 



Concentrated aqueous solution of methylene-blue 40 



0.5 per cent, solution of eosin in 70 per cent, alcohol. .20 

 Distilled water 40 



.* " Deutsche med. Wochenschrift," 1892, 2 ; "Zeitschrift fur Hygiene," 

 13- 



t "Centralbl. f. Bakt.," etc., Bd. xiv, p. 860. 



