119 



parations referred to, and blood, or blood corpuscles will split 

 off some „V" on heating (best seen in agar or broth), while 

 „X" continues to be present in large quantities. The same 

 thing may take place in other ways: Treatment with strong 

 acid (Fleming), digestion with trypsin (Matthews) or pepsin- 

 hydrochloric acid (Fildes). 



We can naturally know nothing of the relation of the two 

 components in intact erythrocytes, because in media containing 

 whole blood corpuscles only those substances which diffuse 

 out into the medium itself, have any effect upon the growth 

 of Pfeiffer's bacillus. If the blood corpuscles are not exposed 

 to destructive actions in preparing the medium there will pre- 

 sumably be only a very small quantity of these substances 

 outside the corpuscles, especially just after the medium is made, 

 and the weak growth of Pfeiffer's bacillus on ordinary blood 

 agar is then easy to understand. This microbe is unable to 

 liberate the erythrocyte's store of haemoglobin with the help 

 of haemolytic substances. 



In blood agar, that is agar containing whole blood cor- 

 puscles, it seems in some cases to be the „V substance that 

 (outside the blood corpuscles) is in excess. Brown & Orcutt, 

 and Skajaa for instance, found that on blood agar only hae- 

 molytic bacteria (which furnish dissolved haemoglobin from 

 the blood corpuscles and consequently the „X" substance) can 

 produce increased growth of Pfeiffer's bacillus, while the non- 

 haemolytic (which only act by providing the „V" substance) 

 are inactive. Skajaa found the same non-haemolytic strains 

 to be active on a medium containing dissolved „haemoglobin" 

 which may be assumed to contain „X" in excess. 



In other cases „X" is present in blood agar in excess, 

 as non-haemolytic bacteria can also increase the growth of 

 Pfeiffer's bacillus on this medium (Davis (5), Jordan (2)). 



As far as they have been investigated, the blood derivatives 

 that act like „X" also give a reaction with guaiac and benzidin. 



Thjotta & Avery (2) found (as mentioned on p. 102) that 

 raw potato was effective when it was the sole addition to 

 broth or Uschinsky's fluid. It thus contains both „X" and 

 „V" as it was inactivated by autoclaving but was again made 

 active by the addition of yeast extract. In harmony witli this 

 it gave the benzidin reaction. 



