Glucose and Mannitol by B. coli communis. 



475 



and mannitol. Two varieties of selected organisms have been used — the 

 one (CI selected) produced from the typical B. coli (Escherich) No. CI, like 

 the organism of Harden and Penfold (1912), produced acid and no gas from 

 glucose, while it still produced gas from " mannitol, and also retained the 

 power of decomposing formates in the presence of glucose (see Grey, 1914). 

 The other (CF selected), obtained from the organism CF, now gave acid but 

 no gas, either from glucose or from mannitol, and was also unable to decom- 

 pose formates even in the presence of glucose. This second selected organism 

 might perhaps be regarded as representing a further stage of selection than 

 the first, but I have not found it possible so far to obtain from CI a strain 

 comparable to CF (selected). 



The Relationship between the Normal and the Artificially Selected Strains 

 as established by the Agglutination Reaction. 



The artificially selected strains (when made into an emulsion by the 

 addition of normal saline to an agar growth) were found in many cases to 

 agglutinate spontaneously. The freshly selected strain was therefore first 

 plated out on plain agar and agar slopes made from several individual 

 colonies. By this means it was found possible to obtain strains which did 

 and strains which did not agglutinate spontaneously. The latter were then 

 treated with rabbit serum containing the specific agglutinins for the normal 

 strains CI and CF, and it was found that the serum obtained by inoculating 

 a rabbit with normal CI agglutinated normal CI and the artificially selected 



Table II. — Demonstration of the Eelation between the Normal and Artificial 

 Selected Strains (obtained by the Chloroacetate Method) by means of the 

 Agglutination Test. 



Bacterial emul- 



Dilution of the serum. 



sion made with — 



1/100. 



1/200. 



1/400. 



1/800. 



1/1600. 



1/3200. 



1/6400. 



1/12800. 



1/25600. 



1/51200. 







Serum obtained with CF normal. 









CF (normal) 

 CF (selected) 

 CI (normal) 

 CI (selected) 



4-4 4 

 4 4 4 



4-4 4 

 4 4 4 



4 4 4 

 4 4 4 



4 4 4 

 4 4 4 



4 4 4 

 4 4 4 



4 4 4 

 4 4 4 



4 4 4 

 4 4 4 



+ + 



+ 4 



+ 4 

 + + 









Serum obtained from CI normal. 









CI (selected) 

 CF (normal) 

 CF (selected) 



+ + + 



+ 4 + 



444 

 4 + 4 



4 4 4 



+ + + 



4 4 4 

 4 4 



4 

 4 













