INFLUENZA 415 



Influenza 



A minute bacillus was first described in this disease 

 by Pfeiffer in 1892, who found it in large numbers in the 

 bronchial secretion. In order to isolate the organism a 

 patient with bronchial expectoration should be chosen ; 

 he rinses his mouth and gargles his throat with hot water 

 several times, and then, after coughing, the expectoration 

 is obtained. A little of this expectoration is washed by 

 shaking in a test-tube with sterile salt solution, then 

 repeating the washing with sterile salt solution in a second 

 and finally in a third test-tube. By means of a platinum 

 needle a number of glycerin- agar and blood- agar tubes 

 are inoculated with the sputum after the last washing, and 

 incubated at 37 C. 



Morphology. The influenza bacillus is one of the smallest 

 bacilli with which we are acquainted. It is a minute rod 

 0-5-1-5 jji in length, and is non-motile and non-sporing. 

 It does not stain by Gram's method, and not very readily 

 with the ordinary dyes, dilute carbol-fuchsin or prolonged 

 staining with Loffler's blue yielding the best results, the 

 poles tending to stain more deeply than the centre. In 

 the sputum it occurs singly, in short chains, in small groups, 

 or in larger masses, being most numerous early in the 

 acute stage of the disease. 



Cultural characters. The bacillus is strictly aerobic, 

 and no growth occurs on media at 22 C. On glycerin- 

 agar and blood-serum at 37 C. it forms very small, trans- 

 parent, drop-like colonies in from twenty-four to forty- 

 eight hours, which, according to Kitasato, never became 

 confluent. There is no growth on potato. The organism 

 grows best on media containing blood, such as agar smeared 

 with sterile human, rabbit's, or pigeon's blood. In broth 

 it grows at the surface in fine white flakes which subse- 

 quently sink. 



