14 
The time of exposure was nineteen hours, the temperature of the ^ 
room being 75° to 85° F. ■' 
The mosquitoes and cultures were exposed in the small pill boxes i 
under exactly similar conditions as follows : 
I 
1 
Mosquitoes. ! 
Bacteria. ' 
Dead, 
Alive. 1 
Subtilis 
spores. 
Pyocya- 1 
neus. |; 
In pill boxes : 
Exposed to the gas without protection 
5 
! 
0 
-f- d 
i 
Under 2 layers of dry toweling 
5 
0 
-f 
— 
Wrapped tightly in a dry towel, 8 layers 
6 
0 
+ d 
— 
Under 2 layers of damp toweling 
8 
0 i 
-b 
— 
Wrapped tightly in a damp towel, 8 layers 
2 
3 1 
-b 
— 
In pocket of a linen coat, hung on wall 
4 
0 , 
+ 
— 
In pocket of duck trousers, folded and laid on floor with 
pocket down 
2 
3 
+ 
_ 
In pocket of trousers, hung up, pocket to wall 
1 
3 
+ 
— 
In corner of a folded newspaper, under 7 layers 
4 
0 
-f 
— 
Under 1 yard of toweling, heaped loosely in a pile..,. 
0 
5 I 
4* ct 
— 
In canvas mail sack, mouth tied 
6 
0 i 
+ 
— 
In bottom of a battery jar under 2 layers of toweling 
7 
0 ! 
+ 
a Delayed. 6 Contaminated. 
Here an excess of about 3 times the usual amount of formalin solu- j 
tion was used, and the time of exposure was nineteen hours. Under \ 
these severe conditions, most of the mosquitoes succumbed. The only | 
survivors were found under exceptionally severe conditions, such as i 
under a heap of towels, or through 8 layers of moist towels, or in ^ 
the pocket of trousers, folded and laid on the floor with the pocket ■ 
down. The gas penetrated in sufficient strength to destroy all the non- i 
spore-bearing bacteria exposed under .precisely the same conditions in 
boxes alongside those containing the mosquitoes. None of the dry , 
spores were killed. 
It is evident from these tests with the autoclave that the time of expo- 
sure is a very important factor in obtaining penetration of the gas to the 
insects protected in fabrics, etc. 
Large percentages of gas for a short time will not penetrate ; neither 
do the conditions prescribed by the United States quarantine regula- 
tions appear to be effective in penetrating to insects deeply hidden, I 
while the long exposures to a large percentage of gas gives but moder- ] 
ately satisfactory results, as far as penetration is concerned. The mos- 1 
quitoes directly exposed to any of these conditions are all killed in a : 
very short time. ' 
While it is by no means absolute, the similarity between the resist- , 
ance of spores and mosquitoes to formaldehyd disinfection is very striking, i 
In other words, to be sure of killing mosquitoes in an ordinary room, 
containing fabrics where the insects may hide, we must use a concentra- 
tion of the gas and a length of exposure sufficient to kill a spore-bearing 
organism. 
