176 
C. A. LUDWIG 
passing through a rubber stopper. The stopper was immediately put 
in place in the tubulature of the bell jar which served as the chamber. 
The liquid then evaporated and diffused to all parts of the chamber, 
as was amply evidenced by the effects on the cultures. The volume 
of the jar was approximately 3.8 liters. 
In the first trial no measure was secured of the amount of methyl 
iodide used; but it was considerably more than in the second, where 
the amount was limited to 5 drops. The results with the different 
species used were so nearly alike that they will not be discussed sepa- 
rately. The species tested were Bacillus subtilis, B. pyocyaneus, B. 
Kieliensis, B. rubidus, Sarcina lutea, Oidium lactis, Cryptococcus 
Ludwigi, and Penicillium stoloniferum. 
Without exception the culture was killed in the test with the larger 
amount of methyl iodide, i. e., there was no development during a 
7-day exposure nor within a period of 24 days after. With the smaller 
amount of the chemical the development was nearly normal in all 
cases except that there was a slight slowing down of the growth, capable 
of detection, however, only for periods of i to 4 days. In addi- 
tion, the pink yeast was slightly pale in color and B. rubidus (on potato) 
was clear yellow instead of orange yellow. 
In the third test six drops of the liquid were used and in the fourth 
something more than ten. The organisms used in these two tests 
were Bacterium stewarti, B. tumefaciens, Bacillus carotovorus, B. 
melonis, B. campestris , B. solanisaprus, B. mycoides, and Pseudomonas 
radicicola. 
The development was uniformly greatly inhibited at first but soon 
began to proceed rapidly so that in the first experiment the treated 
cultures overtook the checks in about 4 or 5 days on the average. 
In the second trial, in which the amount of the chemical was doubled or 
more than doubled, the inhibiting effect was more permanent. Thus 
Bacillus melonis, B. solanisaprus, and Bacterium tumefaciens were the 
only ones to recover and develop as fully as in the air by the close of a 
6-day exposure. Bacillus mycoides would probably have shown an 
equal ability had inoculation been by means of a streak, as the develop- 
ment near the point of inoculation (the center of the slant only) did 
show such an ability. The organism, however, showed a reduction in 
the power to invade the surface of the substratum in the vapor. 
The general effect of methyl-iodide vapor on the organisms tested 
therefore, as shown by the data presented above, is to induce an initial 
