Cultivation 463 



in widely scattered but dense clusters. They are frequently inclosed 

 within the leukocytes. It is scarcely necessary to pursue so tedious 

 a staining method for demonstrating the bacilli, for they stain well 

 enough for recognition by ordinary methods. 



Isolation. — The influenza bacillus grows poorly upon artificial 

 culture-media, and is not easy to isolate, because the associated bac- 

 teria tend to outgrow it. When isolated it is diflScult to keep, as it 

 soon dies in artificial cultures. 



Pfeiffer found that the organism grew when he spread pus from 

 the bronchial secretions upon serum-agar. Subcultures made from 

 the original colonies did not "take." By a series of experiments he 

 was able to make the organism grow when he transferred it to agar- 

 agar, the surface of which was coated with a film of blood taken. 



Fig. 174. — Bacillus of influenza. Smear from sputum (after Heim). 



with precautions as to sterilty, from the finger-tip. Later it was 

 found that the addition of hemoglobin to the culture- medium was 

 equally efficacious. By. the use of such blood-smeared agar and 

 glycerin-agar the organism can now be successfully cultivated. 

 The isolation is best achieved through the use of bronchial secre- 

 tions, carefully washed in sterile water or salt solution to remove 

 contaminating organisms from the mouth. 



Cultivation. — Upon blood-spread glycerin agar-agar, after twenty- 

 four hours in the incubator, minute colorless, transparent, dewdrop- 

 like colonies may be seen along the line of inoculation. They look 

 like condensed moisture, and Kitasato makes a special point of the 

 fact that they never become confluent. The colonies may at times 

 be so small as to require a lens for their detection. 



No growth takes place at room temperature. The organisms die 



