232 



is first inoculated with the air coccus and after a couple of 

 days in the incubator and the addition of the haemoglobin 

 solution, is filtered through a Berkefeld filter, a better growth 

 can be obtained than in ordinary haemoglobin broth. A few 

 other observations will be referred to in connection with the 

 following summary of the literature on the different media. 



A considerable number of modifications of media for Pfeif- 

 fer's bacillus have been introduced in the course of time and 

 particularly during the last pandemic. Most of the media which 

 were tried in the first few years (Huber's agar with Hommel's 

 haemologen, Nastiukow's egg-yolk medium', Cantani's (1) semen 

 medium, Gijon & Preyss's (1) use of haematin agar in con- 

 junction with growth-promoting bacteria, Fichtner's sputum 

 agar), are now obsolete. 



It must also be remarked that various media which were 

 used by Tiijotta, Rivers and others in the study of the nu- 

 tritive requirements of Pfeiffer's bacillus, have no practical 

 importance apart from those cases where these conditions are 

 being investigated. 



The generally useful media may be divided into the 

 following groups: 



1. Agar smeared with blood. 



2. „ mixed with undissolved blood without heating. 



3. „ ,. „ haemolysed blood. 



4. Media where the effect of blood and growth-promoting 

 bacteria are combined. 



5. Agar with heated blood. 



6. „ „ blood altered by the action of acid or alkali. 



7. „ „ pepsin-digested blood. 



8. „ „ trypsin-digested blood. 



9. Selective media. 



10. Media which are particularly suitable for preserving the 



cultures alive. 

 The reason agar receives so much attention in this summary 

 is because solid media have been used to the largest extent 



