BY B. GREIG-SMITH. 



93 



amounts of CO2 evolved, however, indicated that the test bark was probably not 

 sterile, and an examination on the second day showed that this was the case. 

 The gas-t'orming rod with terminal spore was found, not in the loose water, of 

 which there was very little, possibly 2 c.c, but in the fragments of bark and it 

 was only in contact with these that growth occurred on the agar slopes. The 

 control bark was sterile. There was no need to seed the test flask for it already 

 contained the active organisms. 



The amount of CO2 given off from the test was considerable and this with- 

 out the addition of alkali or other substance. The small amount given off from 

 the control, showed that what had previously been considered to be a chemical 

 production of CO2 was in all probability largely due to the activity of the bac- 

 teria in the supposedly sterile but actually non-sterile bark. 



After the gas from the test flask reached the peak on the third day, the 

 yield slowly fell and, on the sixth day, it was considered that the experiment 

 had shown all it could under the conditions. 



In the tirst experiment with the alley-bark, the addition of sodium hydrate 

 had led to no increase in the evolution of CO2, a circumstance which was in 

 marked contrast with the tan-bark. The liarks undoubtedly look different, and 

 the alley-bark is more of the nature of chai'coal, being black and brittle. Chemic- 

 ally the alley-bark absorbs more alkali from the earthy bases and bicarbonates 

 than tan-bark and, if the fermentation of the latter is influenced by the addition 

 of alkali, the alley-bark should also be favourably assisted. The inactivity of the 

 alkali in the tirst experiment was peculiar, but possibly there had not been 

 enough added. The tan-bark was favourably influenced by three-quarters of the 

 alkali capable of being absorbed from bicarbonate in live days. In the same 

 ratio, .30 gi'ams of alley-bark should be influenced by 30 c.c. of normal alkali 

 and it may Ije that the amount added in the first experiment, viz., 16.4 c.c, was 

 not enough to produce any effect. But as 30 c.c. seemed a large quantity to 

 add, it was decided to add 25 c.c. of N/1 sodium hydrate to each flask and see 

 what happened. 



Notliing did Iiappen; the yield continued to fall. Next day a further 5 c.c. 

 of sodium hydrate was added, making the total alkali in each flask 30 c.c. Two 

 days afterwards the experiment was concluded as no increase in the CO2 pro- 

 duction had ensued. We must conclude that alley-bark is not influenced by the 

 addition of sodium hydrate and differs from tan-bark in this respect. The con- 

 trol on the 7th day was sterile, while the test was replete with living bacteria. 



Evolution of Carbon Dioxide form Alley-bark. 



