244 Prof. M. C. Potter. Bacteria as [Jan. 18, 
A further test in confirmation of the above was afforded by an artificial 
imitation of the conditions. About 5 grammes of freshly-heated charcoal 
was exposed to a partial vacuum in the manner before described, in two 
Cloéz flasks. One of these was filled with CO, and the other with air free from 
CO. After standing for 24 hours a stream of air freed from CO, was 
drawn through each of the flasks, and all traces of CO, would thus be 
effectively removed. About 5 cc. of weak hydrochloric acid was then 
introduced into each and connections made as speedily as possible with the 
Reiset absorption apparatus. After the lapse of 24 hours the first flask 
showed that 34 milligrammes of CO, had been given off from the charcoal, 
and in the second flask only 2 milligrammes, this small amount being possibly 
due to some residual carbonates which had escaped reduction in the charcoal. 
As the analysis of ordinary wood-charcoal gives about 3 per cent. of 
ash, and lime is one of the chief constituents, the above readings are in 
agreement with the amount of lime normally present in the charcoal and 
also with the amount of CO, given off from the research-flasks (inoculated 
with bacteria) when treated with weak hydrochloric acid. This further proves 
the truth of the supposition that CO2 is only evolved after the calcium oxide 
has been converted into the carbonate. 
Control experiments made with distilled water inoculated with bacteria, 
without any charcoal, etc., gave no evolution of COs, thus disposing of any 
criticism which might suppose the carbonic acid to be derived from the 
bacteria themselves, and not necessarily from their action upon the amorphous 
carbon. Moreover, the evolution of COs is not confined to the duration of 
the first experiment, and subsequent titrations made from the same material, 
which had been returned to the incubators for a further period, invariably 
demonstrated a further production of COs, thus indicating a continuous 
process of evolution. 
Hlectrical Method of Determining a Rise of Temperature. 
Since the phenomenon of oxidation is accompanied by an evolution of 
heat, it follows that if charcoal were undergoing oxidation it should be 
possible to detect any rise of temperature due to this process. The amount 
of CQz evolved, however, being small during the period of observation, the rise 
of temperature to be expected would at most be only a fraction of a degree. 
In order to discover whether there was any difference in temperature 
between the sterile and inoculated charcoal, the apparatus shown in the 
figure was designed. It consisted of two specially constructed flasks con- 
nected with a thermopile and placed in an incubator, with leads passing 
through a perforation in the side of the incubator to a galvanometer. 
