134 



The same 

 on each 

 medium 



The haemolysis therefore had nothing to do with the sym- 

 biosis effect. The coincidence between strong haemolysis and 

 absence of symbiosis effect is not general because in the pre- 

 vious experiment the opposite was observed in the case of 

 Streptococcus. 



That the symbiosis effect cannot be explained on the ground 

 that the reaction (hydrogen ion concentration) of the medium 

 is altered in a favourable direction, is sufficiently evident from 1 

 the fact that growth-promoting organisms are encountered 

 among alkali-producers as well as among acid-producers. Various 

 other experiments prove the same thing. Thus the same hae- 

 moglobin agar on which typical Pfeiffer's bacilli constantly gave 

 a vigorous symbiosis reaction, was prepared with a series of 

 different reactions. Within a somewhat wide (optimal) range 

 (P H . about 7 — 7.7) Pfeiffer's bacillus grew in pure culture with 

 about the sam'e weak intensity which is usual on this medium, 

 — many times weaker than what is called forth by the sym- 

 biosis effect. (Compare Ghon & Preyss (1) and others, who 

 found that Pfeiffer's bacillus in symbiosis culture tolerated 

 a greater degree of acidity and alkalinity than in pure culture). 



The fact that the growth-promoting power is widely di- 

 stributed among bacteria and has no connection with the spe- 

 cialised functions of individual species or strains, fits in well 

 with the interpretation given above, — that the effect is due 

 to quite an „unspecific" substance, which is exceedingly widely 

 distributed throughout the animal and vegetable kingdoms. 



When the „V" substances from' two such widely different 

 sources as bacteria and the animal organisms, seem to be 

 identical, we should so much the more expect that the same 

 would be the case with the growth-promoting substance from 

 different species of bacteria. The question ought however to 

 be examined a little more closely. If we wish to employ the 

 symbiosis reaction in the characterisation and classification 



