TOBACCO SMOKE AND GROWTH OF MICROORGANISMS 1 75 
Bacillus solanisaprus . — The presence of smoke, either washed or 
unwashed, proved to be a hindrance to the growth of this organism, 
with the washed smoke, as usual, exhibiting the less toxicity. 
Pseudomonas radicicola. — There was little difference between the 
behavior of Ps. radicicola and of the other bacteria in smoke. In the 
first trial the colony was still confined to the lower half of the slant in 
the raw smoke at the end of the exposure, while in the second no growth 
had taken place. In the treated smoke the growth was more vigorous 
and the colony extended the entire length of the slant. 
Bacillus mycoides. — In the case of B. mycoides there was in one 
case no development in raw smoke and in the other the colony was 
pretty closely confined to the base of the slant. In washed smoke 
the colonies had spread nearly or quite over the surface of the agar by 
the time the experiment ended. 
It should perhaps be remarked here in connection with the cultures 
mentioned above that whether specific mention has been made of the 
check cultures in air or not, it is to be understood that they were made, 
that they grew promptly (visible within a day), and that they grew 
over the entire length of the slant. 
It thus appears that tobacco smoke is more or less toxic to the 
organisms used, although it does not seem to exert such extreme 
toxicity to them as it does to some phanerogams. In view of the very 
complicated and variable mixture of compounds which constitute 
smoke, it is hardly worth while to venture an opinion as to which sub- 
stance or group of substances exerts the toxic influence. It may not 
be beside the mark, however, to call attention to the fact that the 
washed smoke was uniformly less toxic in the tests than was the un- 
washed smoke, and to suggest that something capable either of being 
condensed or of being dissolved in water has some part in inducing the 
reactions. 
Methyl-Iodide Vapor 
The use of methyl-iodide vapor as a test gas for organisms was 
undertaken as a test of the reliability of some results obtained from 
methane prepared from methyl iodide by means of the copper-zinc 
couple.; as it was feared that the gas so produced contained some unde- 
composed methyl-iodide vapor. In the experiments with methyl 
iodide the chemical was introduced into the culture chamber by drop- 
ping the liquid on a bit of absorbent cotton supported by a glass rod 
