CHAPTER XVII 

 INFLUENZA 



BACILLUS INFLUENZA (R. PFEIFFER) 



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

 enous, non-liquefying, non-chromogenic, aerobic, pathogenic bacillus, staining 

 by the ordinary methods, but 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 conformed, in large part, to the require- 

 ments of specificity. 



Morphology. The bacilli are very small, having about the same 

 diameter as the bacillus of mouse septicemia, but only half its length 

 (o. 2 by o. 5 n) . They are usually solitary, 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 andLofHer's alkaline meth- 

 ylene 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 demon- 

 stration 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 



The cover-glasses are immersed in the solution, and kept in the 

 incubator for from three to six hours, after which they are washed in 

 water, dried, and mounted in Canada balsam. By this method the 

 erythrocytes are stained red, the leukocytes blue; and the bacilli, also 

 blue, appear as short rods or as dumb-bells. 



Large numbers of bacilli may be present, though sometimes only a 

 few can be found after prolonged search, as they are prone to occur 



* "Deutsche med. Wochenschrift," 1892, 2; "Zeitschrift fur Hygiene," 1893, 

 xiii, 357- 



f'Cehtralbl. f. Bakt.," etc., Bd. xiv, p. 860. 



462 



