2
and easily mixable with water. Used in the dilution of 1 i n 1 0 w h i c h i s r e c o m m e n d e d I h a v e
found it far less effective than 1 in 25 dilution of refined oil emulsion and its cost works out
considerably higher.
Of the effectiveness of emulsions of refined oil I had already been struck in operations
against the larvæ of mosquitoes. The use of a suitable emulsion therefore seemed likely- to be
very effective againt fleas and experiments were commenced with a view to ascertaining the best
way to make emulsions and their relative effectiveness, Since commencing these experiments
Captain Glen Liston, informed me that there is already an emulsion of kerosine on the
market called " Plunas " which costs Rs. 3-8-0 per gallon and is stated to be effective in a
fifty fold. dilution. A sample of this substance was forwarded by him and. its action upon fleas
has been tried in this laboratory. I am inclined for various reasons to believe that Plunas is
an emulsion made with mucilage which may account for its cost. Whatever may be the means
used it is an excellent emulsion mixing at once with water to form a milky fluid and showing no
tendency to separate into its component parts. It is however very costly and the making of
a similar emulsion at a cheaper rate is I am told engaging the attention of the Bombay Labo-
ratory. In the meantime I have been able to prepare on a scale suitable for manufacture an
emulsion equal in every respect to Plunas containing over 80 per cent. oil at a cost not exceeding
ei ght annas per gal l on. Thi s f or pur poses of descr i pt i on I have t er med "Emul si on A. "
To determine the effectiveness of the different substances their action in various dilutions
upon fleas was tried. Fleas for these experiments were collected without the use of chloroform
from rats killed by a blow on the head. and placed in an inverted bell jar ; after a time when the
fleas commence to crawl on the surface of the fur they are easily caught in test tubes ; to
approach as nearly as possible actual conditions experiments were made by pouring on fleas
in a test tube a small quantity of the fluid to be tested giving one shake and as rapidly as
possible throwing out the contents on to an inclined filter paper, the fleas being kept under
observation until it was certian they would not recover. Other experiments were made by
spraying fleas upon filter paper in inverted bell jars just sufficient to ensure a good wetting and
observing the effect. A certain number were made by momentarily dipping flea infested rats
killed by a blow on the head into the dilution to be tested and then immediately placing them
and a filter paper to drain. The momentary immersion and spraying experiments gave very
similar results and the dilutions found effective in this way are more likely to be found of use
in practice than dilutions effective in such long immersions as are employed by Hossack and
Saigol. When immersion of half a minute or more was tried. the substances were found to act
in much greater dilution than in the other methods—Emulsion A being effective in 1 in 1,000
dilution. The rat dipping experiments show that momentary immersion of articles such as
-clothing in 1 in 50 emulsion would. be perfectly effective.
The details and results of experiments are given in the table, only- those dilutions which
killed every flea being considered effective :—
TABLE A.
Substance.
Dilution.
Nature of
experiment.
Duration of
immersion.
F l e a s u s e d .
F l e a s r e - c o v e r e d .
Effective.
Remarks.
Crude oil cm-
ulsion.
, ,
1-50
1-50
1-50
1-10
1-1.0
1-10
Immersion
...
Spraying...
Dipping ra
Immersion
...
Spraying
...
Dipping ra
Momentary ...
. . .
Momentary ...
...
3
...
3
9
... ...
3
6
...
3
..
No
No
No
No
No
No
A number of fleas escaped
and were alive at end of
15 minutes.
Three fleas left rat and were
alive at end of 15 minutes.
Pesterine
e m -
ulsion.
,,
,,
1-50
1-25
1-25
1.-10
1-10
1-10
Immersion
...
Dipping rat
Spraying
Immersion
...
r
,,
„
Momentary ...
...
Momentary ...
...
,,
...
2
...
7
3
2
3
1
3
0
0
1
NoY e s
. . .
Yes
Yes
No
All fleas killed.
Plunas
...
1-100
1-100
immersion
.
Spraying
30 seconds ...
. . .
3
6
0
6
Yes
No
Appeared dead but re-
covered.