16 
No. 12. 
In the same room of 500 cubic feet capacity 330 grams of sulphur 
(about one-third the prescribed amount) were burned, and the room was 
left closed twenty -four hours. Mosquitoes were exposed and with some 
of them subtilis spores, fresh garden earth, and pyocyaneus germs were 
exposed in boxes under similar conditions, as follows : 
Mosquitoes, 
Bacteria, 
Dead. 
Alive. 
Garden 
earth. 
Subtilis 
spores. 
Pyocya- 
neus. 
In pill boxes : 
On floor, no protection 
1 
! + 
1 
Under heavy carpet 
4- 
On shelf, no protection 
-1- 
+ 
On rafter near ceiling’, no protection 
In corner, folded newspaper 
6 
0 
-f 
+ 
Under 4 thicknesses toweling 
6 
0 
j 


Tn mail sack half full of crumpled paper 
7 
0 
Under 8 layers dry toweling 
5 
0 
Under 4 layers damp toweling 
5 
0 
Tender 8 layers damp toweling 
5 
0 
In pocket duck trousers, rolled up 
6 
0 
Rolled 4 times in damp towel and put in coat 
pocket 
6 
0 
1 
On floor under empty wooden box 
5 
0 
1 
I 
This small amount of the gas killed all mosquitoes and non-spore- 
bearing organisms even under conditions requiring deep penetration. 
No. 13. 
These results with sulphur dioxid were so good that another test 
was made to see whether a very small amount of sulphur with a short 
exposure would be sufficient to kill mosquitoes and leave the non-spore- 
bearing organisms unharmed. 
To this end about 6 ounces (191 grams) of sulphur were burned by 
the pot method in a room of just 500 cubic feet capacity. The room 
was aired one hour after the sulphur was lighted, so that the total expos- 
ure to the gas was one hour. 
The mosquitoes and the cultures were exposed in the pill boxes with 
gauze lids, under similar conditions, as follows : 
Mosquitoes. 
Cultures. 
Dead. 
Alive. 
Pyocyaneus. 
In pill boxes : 
One shelf without protection 
4 
0 
+ 
On high rafter, no protection 
4 
0 
-f 
Under 1 layer damp toweling 
4 
0 
+ 
Under 2 layers damp toweling 
4 
0 
+ 
Under 4 layers damp toweling 
4 
0 
+ 
Wrapped in damp towel, 4 layers 
3 
0 
+ 
Wrapped in damp towel, 8 layers 
0 
4 
+ 
Wrapped in dry towel, 4 layers 
4 
0 
On floor under a dirty sheet 
2 
3 
On floor under a wooden box 
0 
4 
+ 
It is plain that very weak percentages of sulphur dioxid are sufficient ' 
to kill mosquitoes in a short time, even though protected by 4 layers of 
