Glucose and Mannitol by B. coli communis. 



95 



Immediately after the sample of solution has been drawn off into the 

 evacuated flask for the determination of the carbon dioxide dissolved, a 

 much larger sample is withdrawn into the flask A, which is slipped over 

 the tube B, which already supports a rubber stopper. To withdraw the 

 sample the flask A is evacuated, and the tap K is turned so as to shut off 

 the absorption bottles and put the fermentation flask into direct com- 

 munication with the gas-holder M. The vessel IST is raised. ISTow upon 

 opening the cock at C the sample is drawn into A and the hydrogen and 

 nitrogen in M are returned to the fermentation flask. 



The hydrogen can be estimated either by the measurement of the change 

 in volume of the gas or by direct determination. At the end of the 

 experiment, when all the samples of solution have been removed from the 

 fermentation flask, the gases may be displaced by the introduction of hot 

 water through B, and collected in M. 



The arrangement of apparatus is suitable for following the stages of either 

 aerobic or anaerobic fermentations. 



Details of an Miyeriynent in vjJiich the Products of Fermentation have heen 

 Examined oi Successive Stages. 



The experiment was carried out as follows : — A weight of 45'84 grm. 

 of pure anhydrous glucose was dissolved in distilled water and the solution 

 sterilised. This solution was then added to about 3 litres of sterile distilled 

 water in a flask of 5 J litres capacity, in which also was about 40 grm. of 

 chalk contained in small floating sacks. The sugar was thus not sterilised 

 in contact with the chalk. The contents of the flask were cooled to 37° C, 

 and 750 c.c. of an emulsion of bacteria was added. The emulsion of bacteria 

 was made from the surface of agar by means of a solution of potassium and 

 magnesium sulphates. The amount of each introduced finally into the 

 solution to be fermented was 11-6 grm. of potassium sulphate and 3'3 grm. 

 of magnesium sulphate. The total volume of the solution in the flask at 

 the beginning of the experiment was 5100 c.c. The fermentation was 

 allowed to take place at approximately 40° C. The weight of bacteria 

 introduced corresponded to a dry w^eight of 0'61 grm., and the weight of other 

 organic matter washed from the agar bottles was 1'83 grm. 



The number of living bacteria introduced at the beginning of the experi- 

 ment was 5100x217x10^^ or 217 x 10^^ for each cubic centimetre of the 

 solution in the flask. 



At the end of 12 hours from the time of introduction of the bacteria 

 samples of the solution were removed for the estimation of the various 



