128 SUPPOSED INSTANCES [CH. ix 



Horrocks considers may have been due to an invasion by this 

 organism from the gut but was more probably due, in his 

 opinion, to the still further modification of the strain injected, 

 inasmuch as " reversion " apparently took place a few hours 

 later. The disappearance of the B. coli might however be 

 explained on other grounds. The strain of B. faecalis 

 alcaligenes undergoing passage may have been contaminated 

 with B. coli between the second and third passages ; the 

 former organism after its two passages might be expected to 

 be more resistant to the body fluids which destroyed the 

 latter. 



(g) The change from B. typhosus to B. faecalis alcaligenes 

 after growth in the diluted and filtered urine of a typhoid 

 carrier and the further change from B. faecalis alcaligenes 

 to Streptococcus faecalis. 



(Page 238, exp. II.) The sterile filtrate from the urine 

 of a typhoid carrier "S" was again inoculated with B. 

 typhosus the strain used, on this occasion, being a stock 

 laboratory strain "R" of unimpeachable character. The 

 result was similar to that in the previous experiment. Side 

 by side with colonies of typical B. typhosus were found 

 colonies of an organism (" 35 A. Col. 2 ") which corresponded 

 with B. faecalis alcaligenes but possessed a slight power of 

 absorbing agglutinins from antityphoid serum (p. 242). Later 

 the latter organism alone was found and it persisted unchanged 

 for many months. The experiment was repeated in exactly 

 the same way and with the same result, B. faecalis al- 

 caligenes emerging (p. 240, exp. IV). 



These two experiments are simply a repetition of the 

 experiments already discussed, a laboratory strain of B. 

 typhosus being used instead of a carrier strain. 



When the inoculated filtrate used in the first experiment 

 (p. 238, exp. II) was 6 months old, a loopful of it was added 

 to a broth tube and a 48 hours' growth plated on MacConkey's 

 medium (p. 239). Colonies of B. faecalis alcaligenes were 

 again found but with them smaller colonies of a streptococcus 

 closely resembling 8. faecalis. 



The strain of B. faecalis alcaligenes obtained in the 



