INFLUENCE OF ILLUMINATING GAS ON BACTERIA AND FUNGI 1 5 
continuously for 4 transfers in 5 percent, 10 percent, and 25 percent 
gas, 3 transfers in 50 percent, 10 transfers in 75 percent, and 4 transfers 
in 85 percent illuminating gas. 
Bacterium stewarti. — B. steward is an aerobic organism which 
proved to be one of the most susceptible employed. It grew in 5 
percent, 10 percent, 25 percent, 50 percent, and 75 percent of illuminat- 
ing gas; and it was possible to keep it growing continuously in these; 
but the development in the last concentration mentioned was slow. 
A distinct checking effect was always shown at 10 percent and often 
a slight one seemed to be present at 5 percent. In the earlier work no 
development was secured at 75 percent, but later on growth did occur. 
The first development occurred at about the time the gas company 
ceased producing water gas, as was the case with the first development 
of Bacillus pyocyaneus in pure gas. The circumstance was probably due 
to the reduction of the CO content of the gas. No development was 
observed in any concentration used above 75 percent; but only rarely 
did development fail to take place after removal to the air, although it 
was usually 5-15 days in becoming visible and was also usually slight 
or very slight in amount. 
The following organisms were tested once in each of 25 percent, 
50 percent, 75 percent, and 85 percent, and twice in 100 percent 
illuminating gas. 
Bacillus carotovorus. — With this organism there was slight develop- 
ment by the end of a 6-day exposure to pure gas in one test but none 
in the other at the end of an equal period. In both cases, however, 
prompt development followed a return to the air. Growth occurred 
in all the lower concentrations, but it was checked in all; and the 
retardation was still noticeable in the 25 percent concentration at the 
end of the 6-day period. 
Bacillus melonis. — In one case with B. melonis the tube in pure gas 
showed a very slight development at the end of the period. In the 
other, however, no growth was visible although it became so soon after 
the return to the air. Growth took place in all the lower concentra- 
tions but it was much retarded in all. 
Bacillus campestris. — With B. campestris also, development oc- 
curred in all the concentrations used except pure gas, although there 
was distinct retardation in even the 25 percent concentration. In 
pure gas there was no growth in one trial but a possible very slight 
development in the other. In both cases growth occurred after 
