H. WORMALD 235 



• 



however gradually became more definite and in 36 hours after inocula- 

 tion all three media were of a bright red colour which was maintained 

 to the end of the experiment. The sequence of colour changes appears 

 to indicate that the bacillus is at first less vigorous in the presence of 

 lactose than when dextrose or saccharose is the sugar available and 

 this is borne out by the fact that in the earlier stages (up to 24 hours) 

 the dextrose and saccharose media become turbid at a more rapid 

 rate than that of lactose. It is associated too with a corresponding 

 variation in gas production. 



Bubbles of gas appear sooner or later in each of the three solutions 

 after inoculation. Such has invariably been the case except in one 

 experiment where gas failed to appear in two fermentation tubes 

 containing the dextrose solution. With this exception bubbles always 

 began to accumulate at the upper end of the tube {i.e. the inner tube 

 in the case of a Durham's tube or the closed arm of a fermentation tube) 

 usually in 20 — 24 hours after inoculation and are to be observed 

 first in either dextrose or saccharose; dextrose seems to favour the 

 early production of gas bubbles, though their appearance in saccharose 

 solution follows shortly afterwards and may even precede that in 

 dextrose. Gas does not appear in the tubes containing lactose until 

 a few hours later but its production then proceeds at a relatively in- 

 creased rate and continues for a longer period ; consequently the final 

 volume of gas accumulated in the tube is always in excess of that 

 contained in the tubes of dextrose or saccharose. 



Harding and Morse (ii) found that various bacilli of the group of 

 soft-rot organisms gave very variable results when grown in bouillon 

 containing one or other of the three sugars above mentioned, even the 

 same strain does not always give even approximately similar results 

 in different experiments; this may be partly due to variation (in 

 chemical composition and concentration) in the bouillon itself and it 

 would be preferable to employ standard synthetic media for the sugar 

 fermentation tests. The results recorded above were obtained by 

 growing the bacillus in a medium containing peptone (a complex organic 

 substance) in addition to the sugar, and those by Harding and Morse 

 from sugar media prepared with sugar-free bouillon as a basis. 



Repeated experiments with synthetic media containing saccharose 

 as the only source of carbon have yielded no free gas whatever, although 

 turbidity and sedimentation with distinct acidity were produced 

 within 24 hours of inoculation. Thus in the absence of other organic 

 compounds the final gaseous decomposition products of saccharose 



Jo urn. of Agric. Sci. vm 16 



