2 
C. A. LUDWIG 
gas and its separate constituents toward several of these organisms. 
The chief aim of this study was to make such determinations. 
HISTORICAL 
A number of investigations have been carried out to determine 
the reactions of phanerogams to low concentrations of different gases, 
and a smaller number to determine the more fundamental matter of 
the effect on the life processes. They have often been concerned in 
the first instance with smoke injury; and the results in general have 
tended to show, as would be expected, that mineral acid oxides or 
the oxides of toxic elements, as, for instance, arsenic, are decidedly 
toxic under conditions of much dilution in the air. They have also 
shown, as mentioned earlier in this paper, that certain plants show 
a remarkable sensitiveness to certain gases which are ordinarily con- 
sidered to be quite inert. This work will not be reviewed further 
here, as it has only an indirect bearing on the problem investigated. 
A bibliography may be found in papers by Crocker and Knight in 
the Botanical Gazette (i, 2). 
When we come to the lower plants, however, we find that com- 
paratively little has been done along this line. Quite early in the 
history of bacteriology the question of the oxygen relation was worked 
out and methods were elaborated for its study with relation to any 
particular organism. This latter work involved a study of hydrogen 
and carbon dioxide as determining their availabihty for displacing 
the air in anaerobic culture conditions; but the matter of other gases, . 
especially in less concentration than purity, appears. to have seemed 
of little or no importance. There have been some pieces of work 
done, however, which have a suggestive or direct bearing on the 
problem and are therefore worthy of mention here. 
Perhaps the earliest published paper of the kind was by Tassinari 
(15). In this case, the effect of tobacco smoke on several bacteria, 
including both pathogenic and non-pathogenic species, was investi- 
gated. The exposure to the smoke was made by means of a clever 
bit of apparatus in which a drop of the culture was held on a fragment 
of linen and the smoke drawn past it. The strip was then dropped 
into sterile medium and the time required for development noted. 
The check cultures developed uniformly in twelve to twenty-four 
hours. The smoked cultures with only one exception were delayed 
from twenty-four to one hundred hours in development or had failed 
to develop at all at the end of eight to twelve days. 
