E. M. Doidgr 33 



Congo red. Congo red was not reduced, but the dye was 

 absorbed by the superficial bacterial growth as in the case of neutral 

 red. 



Cultures were made in nutrient broth tinted with several other 

 dyes, chiefly in order to determine whether any of these would inhibit 

 the growth of the organism. None of them actually inhibited the 

 growth in very dilute solutions, but growth was feeble in broth con- 

 taining malachite green or cyanin. 



The bacillus grew well in Trypan blue, and completely reduced the 

 colouring matter ; Trypan red was not reduced, but the surface growth 

 absorbed the stain. 



Reduction of nitrates. Nitrates were more completely reduced when 

 the organism was grown in nitrate water than when it was grown in 

 nitrate broth. 



A flask of nitrate water (8, p. 169) was inoculated from a young 

 culture of the organism in nutrient broth and incubated with a control 

 flask at 30° C. for five days. The culture was then divided into four 

 portions, the first two being used to test for the presence of nitrites. 

 There was no reaction for nitrites when tested by the iodine-starch 

 method or with a-naphthylamine and sulphanilic acid. 



A third portion tested with Nessler's solution developed a distinct 

 yellow colour indicating the presence of ammonia. The remainder of 

 the culture was evaporated to dryness and tested for the presence of 

 nitrates with phenolsulphonic acid. There was no reaction. 



The nitrate water in the control flask tested in a similar 

 way , gave a distinct reaction for nitrates but none for nitrites or 

 ammonia. 



The test for nitrate reduction was repeated using nitrate broth 

 (8, p. 143) in place of nitrate water. The culture and control were tested 

 on the fifth day in the manner described above and as before the control 

 was found to contain nitrates but no nitrites or ammonia. The culture 

 reacted strongly both with iodine and starch paste, and with a-naph- 

 thylamine and sulphanilic acid showing the presence of nitrites ; there 

 was no reaction, however, for nitrates or ammonia. 



Fermentation tubes. The organism was grown in fermentation tubes 

 containing 2 % sugar broth, but there was no gas production with any 

 of the carbohydrates used. In one solitary case gas was formed from 

 dextrose and saccharose, but this proved to be due to the presence of an 

 interloper. The vigour of growth in the open and the closed end varied 

 greatly with the composition of the medium. The intensity of clouding 

 Ann. Biol, n 3 



