243 



energy of growth. Some of them, — the specially „atypical" 

 it is true, which perhaps have no particular clinical signifi- 

 cance but which without further reason cannot be disregarded, 

 — were even difficult to keep alive on such haemoglobin agar 

 which produced an extremely rich growth of the majority of 

 strains of Pfeiffer's bacillus. It is thus very probable that the 

 selective media will inhibit the delicately growing Pfeiffer's 

 bacilli even if they do not inhibit the more hardy strains from 

 developing. 



10. Lastly it may be mentioned that Gibson & Bowman, 

 and Legroux & Mesnard have described .media on which 

 Pfeiffer's bacillus only needs subculturing with several weeks 

 interval (broth from minced meat, — minced liver). Lal could 

 keep Pfeiffer's bacillus alive for 132 days on blood gelatine 

 by keeping at 37° in tubes sealed with paraffin. According 

 to Wollstein (4) and Tanaka Pfeiffer's bacillus can also be 

 kept alive in blood broth for many weeks. Concerning Twort's 

 mixed cultures see p, 159. 



I have not however found it preferable to use any of 

 these media but have kept my strains going in surface cul- 

 tures on plates of haemoglobin agar and later on Fildes agar, 

 usually by subculturing every 5th. day, incubating for 1 — 2 days, 

 and then keeping them in the cold room. The certainty in 

 recognising the growth of Pfeiffer's bacillus and any contamina- 

 tions and the convenient subculturing from plate to plate have 

 outweighed any advantage the cultures might have of greater 

 resistance to keeping in test tubes. 



The blood of many different species of animals has 

 been used in the preparation of media for Pfeiffer's bacillus. 

 Practically speaking it is only the blood of mammals and 

 birds that is of importance. (Man, horse, ox, sheep, goat, 

 dog, cat, rabbit, guinea-pig, pigeon, fowl, and duck). It is 

 therefore important to know the significance of using the 

 blood of one or other species. 



Briefly it may be said that when using unaltered or simply 

 haemolysed blood, pigeon blood gives a very good growth, 

 human blood a very bad growth, while the blood of the majo- 

 rity of the other species of animals employed seems to give 

 fairly uniform results. But if the blood is heated or subjected 



16* 



