118 



We will go a step further and autoclave the blood agar. It 

 will then be quite inactive itself, but can be reactivated by 

 bacteria, yeasts and other substances containing „V". 



That Cantani and m'any others have been able to obtain 

 a growth of Pfeiffer's bacillus on ordinary agar without the 

 addition of blood, in the presence of growth-promoting bacteria, 

 may be due to a small content of a substance with a pure 

 „X" effect (hematin?), (see Ghon & Preyss, — cf. p. 102). 



Amorphous haemoglobin (Thalhimer), haemoglobin solu- 

 tion prepared by haemolysing washed erythrocytes and then 

 filtering off the stromata (Pfeiffer (2)), the same haemoglobin 

 solution untiltered, and haemoglobin solution made from blood 

 corpuscles with their coating of serum intact, all have prac- 

 tically the same effect, — they contain „X" in abundance and a 

 considerable deficiency of „V". By using a strong concentra- 

 tion of haemoglobin however there will often be sufficient „V" 

 to give maximal growth (in some cases „V" will be present 

 in such trifling amount that this is not possible). But on de- 

 creasing the concentration, the increase of growth on the addi- 

 tion of ,,V <; in the form of bacteria etc., shows that „V" 

 was present in less quantity that „X". Tiijotta & Avery (2) 

 obtained growth with dissolved blood corpuscles in a haemo- 

 globin concentration of 1 : 10000, but when yeast extract was 

 added a haemoglobin concentration of only 1 : 1000000 was 

 necessary. The content in „V" substance of im'pure haemoglo- 

 bin preparations may perhaps come from leucocytes or blood 

 platelets. This question does not seem' to have been inve- 

 stigated. (Compare a remark in Grassberger (1, p. 475) on a 

 medium made with pus, and Fichtner's sputum medium). 



That the stroma does not play any important part is 

 proved by the fact that haemoglobin solution retains its ac- 

 tivity after this is removed by filtration. 



The chemical nature of the „X" and „V" bodies is far 

 from clear. According to Olsen (3) haematin and haemin act 

 like pure „X", while haematoporphyrin is quite inactive. To- 

 cunaga obtained a rich growth on agar with iron-free globin, 

 prepared from crystallised haemoglobin. 



It seems therefore that both globin and the ironcontaining 

 component contain „X", while „V" is only present in globin. 



Like crystallised haemoglobin, the impure haemoglobin pre- 



