114 



With regard to the second point it is a well-known fact that 

 bacteria often change their nutritive requirements and con- 

 ditions of growth very much on cultivation for a long period, 

 so that after some time they can grow on media on which 

 they could not thrive immediately after they were isolated. 

 In the case of bacteria usually classed with the haemoglobin- 

 ophilic, somewhat similar phenomena may take place also. 

 Bordet's whooping-cough bacillus can, for instance, without 

 any difficulty be trained to grow on ordinary agar which 

 under ordinary conditions it is quite incapable of. If the same 

 were the case for Pfeiffer's bacillus haemoglobinophilia would 

 lose considerably in value as a specific character, or at all 

 events would have to be used with greater caution. 



Pfeiffer (2) had already drawn attention to the importance 

 of this point, having convinced himself that ,,auch die altesten Cul- 

 turen haben keine weitergehende Anpassung an saprophytische Le- 

 bensbedingungen erfahren und gedeihen wie im Anfang ausschliesslich 

 auf Blutagar". Davis, Stillman & Bourn, Wade & AUnalang 

 and others, had the same experience. 



Tocunaga observed that Pfeiffer's bacillus after being cultivated 

 for a long time (10 months) could gradually do with less haemoglobin, 

 but it could never grow on absolutely haemoglobin-free media. The 

 statements of Jundell, Wataguti, and Tocunaga about training 

 Pfeiffer's bacillus to grow on haemoglobin-free, serum-contai- 

 ning media, must, for reasons already mentioned, be regarded as 

 uncertain. 



In the material I have worked with, there has been abso- 

 lutely no evidence that by prolonged cultivation Pfeiffer's ba- 

 cillus may lose its haemoglobinophilic quality, and it seems 

 therefore to be legitimate, as an obligatory character of this 

 microbe, to demand constant haemoglobinophilia in the 

 meaning of the word elucidated above. 



Several authors (Wolff, Marx, Frosch & Bierbaum, Ritchie, 

 Davis (4)) have described bacteria which immediately after isola- 

 tion were markedly haemoglobinophilic, but later lost this charac- 

 ter. There need hardly be any doubt about excluding all such 

 organisms from the designation Pfeiffer's bacillus, as in other points 

 too they diverge from same, so that in demonstrating the latter 

 it is not necessary to repeat the test of haemoglobinophilia after 

 several months 5 ' cultivation, which would also be, as a rule, prac- 

 tically impossible to carry out. We will return later to these tempo- 

 rary haemoglobinophilic bacteria. 



