312 BAQTEBIOLOGY. 



surface of the prepared agar-agar. The plate or tube 

 is then placed in the incubator at 37° to 38° C. If in- 

 fluenza bacilli be present, they will develop as minute, 

 transparent, watery colonies that are without structure 

 and which resemble somewhat minute drops of dew. 

 They are discrete and show little or no tendency to 

 coalesce. 



If a small bit of mucus be rubbed over the surface 

 of ordinary nutrient agar-agar, no such colonies de- 

 velop. In making the diagnosis by this method cul- 

 tures on both agar-agar containing blood (not blood- 

 serum) and agar-agar containing no blood should 

 always be made, for the reason that growth of these 

 peculiar colonies in the former and no such growth in 

 the latter are evidence that one is dealing with mate- 

 rials from a case of influenza. 



It may also be cultivated in bouillon to which blood 

 has been added, if kept at body temperature. The 

 growth appears as whitish flakes. Since this organism 

 is a strict aerobe, its cultivation can only be conducted 

 on the surface of the medium used — i. e., where it has 

 freest access to oxygen. It is therefore inadvisable to 

 prepare plates in the usual way. When its cultivation 

 is attempted in bouillon it is recommended, in order to 

 favor the free diffusion of oxygen, that the depth of 

 fluid be very shallow. 



Contrary to what might be supposed, the bacillus of 

 influenza has very little tenacity to life outside of the 

 diseased body. It is destroyed by rapid drying in 

 from two to three hours, and when dried more slowly 

 in from eight to twenty-four hours. Cultures retain 

 their vitality for from two to three weeks. The 

 organism dies in water in a little over a day. As a 



