247 



24—36 hours. The plates ought however to be examined again 

 after remaining another 24 hours in the incubator. 



For the preparation of large quantities of culture (for sero- 

 logical work or vaccine production) „chocolate" agar seems 

 particularly suitable. 



The reason that the extensive investigations into the oc- 

 currence of Pfeiffer's bacillus during the last pandemic did 

 not bring forth the hoped-for explanation of the nature of 

 the undoubted connection between this bacillus and influenza, 

 depended to a large extent upon the fact that we were still 

 rather groping in the dark as regards the purely elementary 

 technique of cultivation. We must certainly recognise the 

 necessity of again undertaking extensive investigations during 

 another pandemic which will undoubtedly take place sooner 

 or later, but according to a carefully prepared plan and at 

 the same time making use of the experience of the last few 

 years. Besides the special problem of the relation of Pfeiffer's 

 bacillus to influenza, many other questions relating to this 

 organism, particularly its manner of spreading among healthy 

 and diseased persons and the biochemical factors which are 

 important in its cultivation deserve further investigation which 

 will probably also throw light upon questions of more general 

 bacteriological interest. 



In this review of the experiences of myself and others 

 which is now concluded, it has not so much been my object to 

 establish definite conceptions as to display an extensive col- 

 lection of facts. It is my hope that even for those readers 

 who are unable to share my particular views, these experien- 

 ces may form a portion of the material from 1 which further 

 studies can spring. 



