86 



HIGH TEMPERATURE ORGANISM OF FERMENTING TAN-BARK, 



of the fluids led to further additions of alkali, as noted in the table. It was 

 observed that the bark became darker in colour as time went on. 



At the end of the fifth day, the difference in the results was very small and 

 the conclusion was come to that the raw bark was useless for showing the 

 activity of the bacteria. In order to utilise the aj3parat\is pending the arrival 

 of a (juantity of tempered bark, the experiment was continued and it is for- 

 tunate that it was, for the later results showed that under the conditions there 

 was a small but decided evolution of CO2 from the bark impregnated with the 

 bacteria. The repeated additions of alkali gave more liquid than was desired, 

 but this could not be avoided. Were the experiment to be repeated, the weak 

 alkali would naturally not be used. At the end of the eighth day, the test con- 

 tained living bacteria and the control was sterile. 



500 



roo 



10 



IS OAVS. 



Tert-fifj. 1. The Feniientation of Tan-bark. Total yield of Carbon Dioxide. 

 Unbroken line = test, broken line = control. 



From the experimental results and from the curves, one can see that the 

 bacteria were quiescent for six- days and, from that time onwards, they began to 

 attack some constituent of the bark and from it to produce carbon dioxide. 



Thus we have a production of carbon dioxide due to what we may call a 

 chemical oxidation, as evidenced by the control test, and also to a bacterial fer- 

 mentation, as shown by tlie excess of tlic test over the control. On the tenth 

 day, the fluids in the flasks had a slight acidity towards litmus paper. Although 

 it is possible that the repeated addition of the alkali favoui-ed the gi-owth of the 

 bacteria, yet an examination of the curves gives one the idea that it was re- 



