402 APPLICATION OF METHODS OF BACTERIOLOGY 



placed in the incubator at 37° to 38° C. If influenza 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 develop. 

 In making the diagnosis by this method cultures 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 materials from a case of influenza. 



The organism 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, bacterium influenzae 

 has very little tenacity of life outside of the diseased body. 

 It is destroyed in from two to three hours by rapid drying, 

 and in from eight to twenty-four hours when dried more 

 slowly. Cultures retain their vitality for from two to three 

 weeks. The organism dies in water in a little over a day. 

 As a result of these observations, Pfeifler does not believe 

 the disease to be disseminated by either the air or the water, 

 but rather by direct infection from the catarrhal secretions 

 of the patients. 



