CH. ix] OF TRANSMUTATION 137 



B. Aertryck in the faeces of all of them. The remaining 

 guineapigs may have been infected by B. Aertryck from the 

 faeces of these, at one stage or another, owing to their food 

 becoming contaminated. The same factors would explain, in 

 their case, the later appearance of B. Gaertner. 



It is, however, to be noted that at the 1st examination 

 (August 23rd) of the guineapigs in cages A and B, while both 

 those which had been fed with the Gaertner culture were 

 passing B. Aertryck in their faeces, three of the six animals 

 which had not been fed with the Gaertner culture were 

 passing B. Gaertner. To explain this on the grounds that the 

 food of these three had been contaminated by the faeces of 

 the Gaertner fed guineapigs, we must assume that the latter 

 had, at some time previous to the examination, been also 

 passing B. Gaertner in their faeces and that this organism 

 had only later given place to B. Aertryck. 



That the factors we have been discussing do actually lead 

 to the detection in the faeces of organisms which previously 

 did not appear to be present, the writer endeavoured to prove 

 by further experiment. 



Experiment II. On August 25th six apparently healthy 

 guineapigs were chosen and labelled Nos. 1 to 6. A frag- 

 ment of the faeces from each guineapig was shaken up in 

 malachite green broth and after incubation the latter was 

 plated out, two sterile plates being used for each guineapig. 



Both plates from No. 3 showed white colonies. A culture 

 from these colonies was grown in broth for 48 hours and then 

 passed through the sugars by which means it was identified 

 as B. proteus. In the case of the remainder the five pairs of 

 plates all proved to be sterile. 



The guineapigs were then for several days fed on green 

 vegetables and bran soaked in castor oil a diet designedly 

 unwholesome and calculated to make the animals ill and also 

 to set up some intestinal catarrh. On August 30th a fragment 

 of faeces from each guineapig was again shaken up in 

 malachite green broth and this, after incubation, plated out 

 as before on two sterile plates. 



In the case of No. 1 and No. 5 no growth was apparent in 



