372 
Philippine Journal of Science 
1919 
All the blocks treated with 1 per cent solution were seriously 
attacked after the lapse of six months. The blocks that were 
treated with 2 and 3 per cent solutions were also seriously 
attacked, although a small number of them remained in sound 
condition for more than two years. ' By the last inspection it 
was found that the percentage of damage was very much lower 
in the blocks treated with 5 per cent and 10 per cent solutions 
than in those treated with 1 and 3 per cent solutions. 
There is no doubt that the camphor green oil itself is effective 
in preventing the attack of termites. However, when it is used 
in a too diluted condition it is not absolutely effective, the per- 
centage of damage being inversely proportional to the amount 
of the oil contained in the solution. 
Table XXVIII .— Damage done by termites to Japanese pine blocks treated 
with different percentages of camphor green oil solution. 
Percentage of damage to blocks containing — 
Length of exposure to termites. 
1 per cent 
of oil. 
2 percent 
of oil. 
3 per cent 
of oil. 
5 per cent 
of oil. 
10 per 
cent of 
oil. 
6 months 
100 
89 
76 
19 
7 
90 
90 
44 
36 
94 
90 
49 
37 
31 months.. 
94 
90 
53 
46 
The amount of the oil that is effective in preventing the 
damage may vary with different kinds of timber. I regret 
that at present I am unable to show the exact amount of oil 
applicable to different Japanese timbers. 
Experiment 3 . — From an economic point of view, it is desir- 
able to use a minimum amount of the camphor green oil; 
therefore, the discovery of an economical, efficient solvent in 
making a dilute solution of the green oil becomes a most im- 
portant problem. For this purpose I have selected a neutral 
oil of petroleum produced from the crude oil obtained at Niizu, 
Japan proper, because it is produced in large quantities at a 
reasonable price ; it is almost colorless, giving no stain to 
timbers ; and it is highly effective in killing the termite. 
The following is the result of the test made to determine the 
exterminating power of various neutral oils. A small amount 
of oil was placed in a watch glass and a worker of Coptotermes 
formosanus was immersed. Under a dissecting microscope the 
motion of the insect was observed and the time at which it 
became motionless was recorded. 
