TOBACCO SMOKE AND GROWTH OF MICROORGANISMS 1 73 
served, however, that a general but less pronounced tendency for this 
sort of behavior existed for the cultures in the other gases; and this 
would seem to indicate that the greater thickness and perhaps moisture 
content of the substratum at the bottom of the slant together with the 
heavier inoculation at the beginning of the streak may have had some- 
thing to do with the results. Apparently the complete prevention of 
growth at the outset would preclude any assumption that the gases did 
not diffuse to the bottom of the tubes. 
The reports for the following eight organisms are based on two 
trials in unwashed and one in washed smoke. 
Bacillus subtilis. — In the first test there was no visible develop- 
ment in unwashed smoke until the sixth day; in the second test it 
became visible on the second day. The retardation continued through- 
out the duration of the 7-day exposure, however, with the washed 
smoke showing the smaller inhibitive effect. The length of duration 
of the retarding effect is a point of some significance, as under some 
circumstances a bacterial culture will show an initial retardation, but 
will reach a stage of development quite indistinguishable from that of 
the check within 3 or 4 days. 
Bacillus pyocyaneus. — In the unwashed smoke, both trials, the 
growth of the organism became visible in one day ; but the colony had 
not entirely reached the top of the slant at the end of the exposure. 
Bacillus Kieliensis. — In the first trial the colony of B. Kieliensis 
had just become visible in 6 days. In the second trial it had become 
visible in 2 days in both raw and washed smoke. By the end of the 
7-day period, however, it had developed upon little more than half 
the length of the slant in raw smoke but over the entire length in 
washed smoke. 
Bacillus rubidus. — In these tests the culture of B. ruhidus was 
made on potato, and there was no test in washed smoke. In the tests 
with raw smoke the cultures required 2 days and 4 days respectively 
to become visible, while the check in air was visible the day after 
inoculation in both cases. 
Sarcina lutea. — The development of S. lutea was hindered by the 
smoke, more so by that which was untreated than by that which was 
bubbled through water; but in all cases the colony occupied all of the 
inoculated area and had produced an abundance of material by the 
close of the 7-day exposure. 
Oidium lactis. — The development of 0. lactis began promptly in 
