726 The American Naturalist. [Agunst, 
alcohol used was the ordinary commercial article (in the neighborhood 
of 95 per cent.), and it may prove that a weaker grade, as likely to 
alter the gelatine less, will answer the purpose better.— H. Garman. 
The Effects of COj Upon Bacteria.— An important paper has 
recently appeared, by Dr. Carl Frankel, on the influence of carbonic 
acid gas upon the life and activities of micro-organisms. ^ Frankel 
was led to undertake this investigation by noticing that the deeper 
layers of soil, when freshly examined, contained very few germs, but 
after standing a few hours became prodigiously rich in bacteria. 
Thus, for instance, a sample of earth taken from the depth of three- 
and-a-half meters was found to hold in one-fiftieth of a cubic centime- 
ter twelve living germs, but in twenty-four hours this number had 
mounted to 40,888. The question therefore arises as to why the mi- 
cro-organisms existing in the lower strata of the soil do not thrive and 
multiply, since they are evidently in the presence of abundant and 
satisfactory food. Plainly there must be some influence in the sub-sail 
distinctly hostile to the development of the bacteria which are there 
present. Frankel suspected that the unfavorable conditions might lie 
in the peculiar composition of the ground air, since this differs from 
ordinary atmospheric air in the smaller amount of oxygen and the 
much larger amount of carbonic acid which it contains. He has con- 
sequently studied the effects of carbonic acid upon micro-organisms 
with a view to clearing up this matter, and to throwing some light on 
the problems of putrefaction. 
After giving the details of a series of skilfully conceived and care- 
fully executed experiments, Frankel briefly sums up his results. 
1. A certain number of the known species of bacteria are able to 
thrive practically as well in CO^ as in ordinary air. 
2. Others, although able to develop in CO^, have their growth de- 
layed and hindered by its presence. 
3. A third group does not grow in CO^ imder ordinary conditions, 
but develops when placed at the incubating temperature [35°-37°]- 
4. The greater part of the rest, including many saprophytic kinds, 
do not thrive in CO3 under any conditions whatever, but are not, how- 
ever, killed, and always develop when the CO^ is replaced by atmos- 
pheric air, even after being subjected to the action of the CO^ for a 
long time. 
Some bacteria. 
among 
them 
the 
t important pathogeni 
Die Einwirkung der 
■krift fur Hygiene, 
Kohlensa 
Till 
^^li 
Leb( 
:nsthatigkeit der Mikroorg 
