Cultivation 48/ 



in widdy 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 bacilU, 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 difficult 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. 173. — 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. The most ready means of cultivation is by 

 the use of i per cent, dextrose agar-agar containing i per cent, of 

 laked, defibrinated human blood. The isolation is best achieved 

 through the use of bronchial secretions, carefully washed in sterile 

 water or salt solution to remove contaminating organisms from the 

 mouth. 



Cultivation.— After twenty-four hours in the incubator, minute 

 colorless, transparent, dewdrop-like colonies may be seen. 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 



