BT R. GREIG-SMITH. 

 Evolution of Carbon Dioxide from Stack-bark. 



95 



On the 8th day, the control was found to be sterile and the test to contain 

 the stout rods with terminal spores. Although the neck and shoulders of the 

 flasks showed water droplets, the barks themselves seemed to be ratlier dry and 

 it was considered advisable to add some water. The. idea wa.*; to add a solution 

 of asparagin, but this was deferred on account of tlic appearance of the barks. 

 They had become too dry, for 10 c.c. of water caused tlie yield of carbon dioxide 

 to go up. By the 11th day the action had slowed down and 10 c.c. of water 

 containing 0.25 gram of asparagin were added to each flask. 



The asparagin increased the yield of carbon dioxide but not to the extent 

 that the earlier experiment with tau-l)ark had led one to expect. But it was 

 certainly curious that the asparagin should increase the gas in the control. This 

 was unexpected and leads one to think that perhaps the control bark was not 

 completely sterilised by the mercuric chloride added in the beginning. It is 

 possible that some parts of the bark missed the action of the disinfectant and, if 

 this is the reason, we must consider that the comparatively small yield of carbon 

 dioxide by the control may be due, not to a chemical oxidation, but to a re- 

 strained bacterial fermentation. Tubes of saccharose media rubbed with frag- 

 ments of the control liark gave no gxowths so that, as far as one can judge, the 

 bark was sterile. 



The experiment showed that 30 grams of dry stack-bark, when fermented 

 with the native bacteria, gave off an excess of 1.25 grams of carbon dioxide in 

 11 days, and with the addition of 0.25 gram of asparagin a further excess of 

 0.37 gram in 5 days. 



A fermentation experiment was made with viscose and Uschinsky's solution, 

 but no carbon dioxide was given off during three days. A small quantity of 



