C. W. Howard 
167 
in the hold of the ship used. In addition to this several honey jars containing 
engorged female Blue Ticks, and with mosquito netting tied over the tops, were 
placed in various parts of the hold, top and bottom, fore and aft, to ascertain 
whether the gas was of equal strength in all parts. 
In this experiment all the ticks perished except one engorged 
female Amblyomma hehraeum, from the preparation where the ticks 
were placed between boards with hay packed between. This tick 
appeared dead at first, but subsequently produced a quantity of eggs 
nearly normal in number, although she did not retain vitality enough 
to move about. The eggs were kept under observation and several 
of those first laid hatched, while at the last examination the developing 
embryos could be seen in many others. The percentage of eggs 
retaining their vitality was, however, comparatively small. The eggs 
subjected to the gas never hatched but soon shrivelled up, whereas 
the check lots hatched in due time. 
Owing to the fact that the ticks in the above experiment had been 
unavoidably subjected to the Clayton gas for more than twelve hours 
it was determined to try another smaller experiment to see if twelve 
hours’ exposure to 15 “/o of the gas was quite sufficient to de.stroy the 
ticks. Accordingly the test was made on March 6th. The species 
and stages of ticks employed were the same as in the previous test. 
Only the preparations with ticks in the bale of hay, box of sawdust, 
wrapped in three sheets of brown wrapping paper and placed inside 
a shoe box, and the jar containing ticks wrapped in cotton wool, were 
employed. On March 23rd after several examinations it was found 
that every tick had been killed. 
We must conclude from these trials that the Clayton gas (SOo) 
is effective in killing ticks in the holds of cattle ships, when closed 
tightly, and is able to penetrate fairly dense substances. While, 
however, it is effective in destroying or preventing movement of live 
ticks, it is not absolutely effective in destroying entirely the vitality 
of engorged female ticks, so that an occasional one may survive to lay 
eggs, a portion of which may hatch. The system is therefore effective 
in cleaning ships from diseases which are transmitted from one stage 
of the ticks to the other, but where the disease can be transmitted 
through the eggs it is not entirely effective. 
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