6 
1 
were sprayed on the sheets and the room was closed. This room has 2 
doors and 4 windows, is of wooden construction, and rather leaky. The 
windows and doors were simply closed and no pasting or calking was 
done. Time of exposure, six hours. 
Mosquitoes. 
In battery jar one-tMrd full of absorbent cotton and crumpled toweling.. 
In pill boxes — 
1. In single fold of a towel 
2. In double fold of a towel ‘ 
3. Polled loosely in a towel 
In large test tubes — 
1. Very thin layer cotton tied over mouth 
2. Very thin cotton stopper 
3. Ordinary cotton stopper, inches 
4. Large cotton stopper, 24 inches 
Dead. Alive. 
0 12 
0 3 
0 2 
0 3 
1 0 
0 1 
0 . 1 
0 1 
In order to compare the effect upon mosquitoes with the germicidal 
power of the gas, bacteria were exposed at the same time as follows : 
Garden 
earth. 
Subtilis 
spores. 
Anthrax 
spores. 
Staphy- 
lococcus. 
Pyocya- 
neus. 
Icter- 
oides. 
In envelopes, not sealed 
+ 
_ 
_ 
- 
In Petri dishes 
+ 
— 
— 
— 
— 
— 
In paper boxes, perforated ends 
-h 
+ 
~T 
— 
— 
— 
Note. — Throughout these experiments means growth, and — no growth. 
From this experiment it appears that the formaldehyd was strong 
enough in the six hours’ exposure to kilt all the non-spore-bearing organ- 
isms and some of the spores, but that it had no effect upon the mosqui- 
toes, protected as they were by various layers of towel or cotton. 
As the insects and the bacteria were not exposed under precisely 
similar conditions, the following experiment was made : 
I 
No. 2. I 
[ 
The conditions of this experiment were similar to those of No. 1, 
excepting the time of exposure was lengthened to twenty hours. The 
same room of 2,000 cubic feet capacity was used and 20 ounces (600 c.c.) 
of formalin (40 per cent) were sprayed upon 4 sheets. 
This time the mosquitoes and the paper slips impregnated with the 
cultures of bacteria were exposed under exactly the same conditions. 
The insects were confined in little pill boxes with the gauze covers 
described above. The slips of paper impregnated with the cultures 
were placed in precisely similar boxes, the only difference being that 
the boxes were sterilized before receiving the slips. One series of boxes - 
contained the mosquitoes, another subtilis spores, and the third pyocya- i 
