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arise from the blood pigment, and haematogen is formed from 

 the ovo-vitellin of egg yolk by digestion, which according to 

 Bunge is of importance in the formation of blood). That 

 Cantani (2) also found cholesterin, egg albumin, serum 1 albumin, 

 and semen active, can be explained partly by activation of the 

 haemoglobin derivative (haematin) in the agar, and partly, — 

 in the case of the last two substances, — that they themselves 

 contained haemoglobin. But the growth-producing power of 

 all these bodies is undoubtedly rather unreliable, and many 

 authors have hardly been able to detect it. 



Opinion is divided as to how far serum or ascitic 

 fluid can replace „haemoglobin". The common view is that 

 Pfeiffer's bacillus cannot grow on agar with the addition of 

 these fluids if they are free from haemoglobin. In explanation 

 of the various reports of the growth of Pfeiffer's bacillus 

 on such media, there is a good possibility that the serous 

 fluid did contain haemoglobin. In most cases this possibility 

 is either disregarded, or it is stated that haemoglobin could not 

 be demonstrated spectroscopically, which assurance is 

 absolutely worthless, because a haemoglobin concentration that 

 is much too small to be demonstrated spectroscopically, may 

 be sufficient to allow the growth of Pfeiffer's bacillus, espe- 

 cially in the presence of other kinds of bacteria. 



On the authority of the literature on the subject it must 

 however be stated that although Pfeiffer's bacillus may be able 

 to grow, in certain cases even in pure culture, on medium 

 containing serum or serous fluids without „haemoglobin", it 

 much prefers the pigments of the blood. 



I will now pass on to report my own experiences of the 

 various aspects of the haemoglobinophilia of Pfeiffer's bacillus. 



This term has a positive side: growth on „haemoglobin ; '- 

 containing media, and a negative side: no growth on „haemO- 

 globin"-free media. 



As regards the positive side I will only remark here 

 that I have certainly not systematically investigated whe- 

 ther the kind of medium is a matter of indifference in demon- 

 strating growth on „haemoglobin" containing media. But every- 

 thing indicates that all the bacteria, which are termed haemo- 



