INFLUENCE OF ILLUMINATING GAS ON BACTERIA AND FUNGI 27 
From these results it would appear that carbon monoxide is approxi- 
mately equal to illuminating gas in the inhibitive effects on the 
organisms tested and considerably more active in this way than 
either methane or ethylene. It would not seem to be sufficiently 
toxic, however, to be the sole cause of the effects produced by the 
illuminating gas. 
5. General Observations and Discussion 
It was noted in the present work, as was of course to be expected, 
that not all organisms showed the same sort of reaction or exhibited 
the same degree of tolerance to the gases. Thus B. suhtilis, B. 
pyocyaneuSj B. mycoides, and B. Kieliensis showed a high degree of 
tolerance for illuminating gas. In the case of B. suhtilis, B. mycoides, 
and B. Kieliensis the colony in the high concentrations was quite 
different in appearance from the normal one. In the case of the 
first two species this is owing perhaps merely to the very small mass 
of material produced, but in the last named it is associated also with 
a decrease in pigment production. However, in the case of B. pyo- 
cyaneus and 0. lactis the appearance of the colony was comparatively 
little altered. Probably the most sensitive of the species studied were 
Sarcina lutea. Bacterium stewarti, and Penicillium stoloniferum. 
Among the group of fungi tested together, Fusarium radicicola was 
the most resistant while Endothia fluens was most inhibited by the 
lower percentages of gas, followed by E. parasitica and Penicillium 
pinophilum. 
The data do not seem to warrant any conclusion that any of the 
strains acquired an increased degree of tolerance for illuminating gas 
by being cultivated continuously in its presence. Such did seem 
to be the case for a time with Bacillus pyocyaneus and Bacterium 
stewarti, but when cultures inoculated with the original mother strain, 
which had not been exposed to gas at all, were exposed to the gas along 
with the supposed acclimated strain, the development of the unaccli- 
mated strain was quite equal to the other. In fact there was some evi- 
dence that continuous growth in.toxic concentrations of the gas weakened 
the organism slightly. This was more clearly evidenced with Bacillus 
Kieliensis, perhaps, than with any other and was shown by the fact 
that the color production was not quite normal for three or four 
transfers in the air after several transfers in pure gas. 
