242 Prof. M. C. Potter. Bacteria as |. [Jane tat 
operation was repeated daily for at least three days. In this manner any 
gases entangled in the charcoal would be removed, and at the same time 
complete sterilisation would be effected. Finally the excess of water was 
removed by evaporation. 
Asbestos plugs, previously heated to redness, were always employed in 
place of cotton wool, as the latter might give rise to COs, and thus become a 
source of error. 
Several sets of apparatus, as described, were set up, and into some of the 
research-flasks bacteria were introduced, while the others were used as 
controls. 
The bactertwm was obtained from the soil. For the purpose of isolation a 
number of test-tubes were partially filled with the reheated charcoal moistened 
in distilled water and sterilised in a steamer. A small quantity of garden 
soil was shaken up with water, and, after allowing the coarser particles to 
settle, about 1 cc. of this water was introduced into one of the test-tubes, 
which was then placed in an incubator at 20°C. After two days a similar 
test-tube was inoculated from the first by means of a loop of platinum wire, 
the process was repeated in a third test-tube, and so on. Those bacteria 
which could not live on charcoal were thus gradually eliminated, and finally, 
by constant inspection, a Dzplococcus, diameter 1 w, was obtained in pure 
culture, which was employed for this research. (There is, however, no reason 
to suppose that this species alone is capable of oxidising carbon, probably it is 
a property possessed by many other species.) 
The bacteria were introduced into some of the research-flasks by removing 
the asbestos plug and pouring in a little distilled water containing the 
Diplococcus. The aperture was then closed as quickly as possible, the 
asbestos replaced, and the whole end of the tube heated to dull redness in the 
Bunsen flame. The inoculated flasks and the controls were then treated in 
a precisely similar manner. The apertures were closed with rubber tubes 
and glass stoppers, and all the flasks placed in an incubator at 20° C.; at 
intervals of a week a stream of air—about 5 litres—was drawn through the 
apparatus, and titrations were made of the baryta water, great care being 
taken to prevent the latter from absorbing any CO, from the air during this 
process. 
For the first week no CO, could be detected in the air from either the 
controls or the inoculated flasks. This result was not encouraging, and at 
this stage of the proceedings it appeared as though the investigation might. 
prove fruitless. However, after nearly another week the air contained in the 
inoculated flasks gave a distinct indication of the presence of COz, The amount 
detected in this way was never large, only amounting to 7 milligrammes: 
= 
