8 
The conditions of this test corresponded about to the requirements of 
bacterial disinfection, the time of exposure being longer than necessary 
to destroy surface infection. 
From this test it is again plainly shown that the formaldehyd gas 
penetrates in sufficient strength to kill a non-spore-bearing organism 
(pyocyaneus) into j)Ockets of overalls or through 1 layer of toweling, 
but not in sufficient strength to kill mosquitoes. There seems to be an 
analogy between these insects and the resistance shown by the spores. 
The fact that some of the mosquitoes die when confined in a little pill 
box for twenty-four hours should not be taken as an indication that they 
were killed by the gas, for mosquitoes thus confined, even under favor- 
able circumstances of moisture and temperature, often die. It is very 
common in our controls to find half or more of the insects dead within 
twenty-four hours; therefore, if 1 mosquito survives the exposure, we 
consider that the death of the others in the same box was not due to the 
effects of the gas. 
Ho. 4. 
This test was made in a small closet with 1 window, capacity, 250 
cubic feet. About 17 ounces (500 c. c.) of wood alcohol were consumed 
in a Kuhn lamp. This is an excess of nearly 4 times the usual quan- 
tity required in disinfection. The room is of fairly tight construction 
and the door and window were closed without sealing or pasting. The 
temperature during the exposure was 82° to 86° F. The time of 
exposure, twenty hours. 
The mosquitoes and the bacteria in this test were exposed in the pill 
boxes to the same conditions, as follows : 
Mosquitoes. 
Bacteria. 
Dead. 
Alives 
Subtilis 
spores. 
Pyocya- 
neus. 
In pill boxes : 
Under 2 layers of damp toweling 
3 
2 
-b 
Under 2 layers of dry toweling 
5 
0 
-f 
— 
In pocket duck coat, hanging on wall, pocket turned to 
wall 
6 
0 
+ 
In pocket duck coat, pocket stands open 
4 
0 
— 
In closed pocket of trousers, hung up 
4 
0 
-f 
— 
Controls, exposed without protection 
3 
0 
+ 
— 
It is evident that even excessive amounts of the gas, such as were 
employed in this test, are not sure insecticides if the mosquitoes are not 
exposed directly to the action of the gas. Note that 2 out of 5 mos- 
quitoes survived under 2 layers of damp toweling. Despite the large 
amount of wood alcohol oxidized in the lamp, there was not enough 
formaldehyd gas generated to kill the subtilis spores exposed as controls. 
