llOO DR. S. II. LONG ON THE MOSQUITO-MALARIA THEORY. 
(4) Certain aniline dyes, the two most potent of which are 
larvicide and gallol, have been proved to cause the death of the 
larvae in from twelve to twenty-four hours in very dilute solution 
(the minimum larvicidal dose in twenty-four hours of larvicide is 
0 '000 15 per cent.). The great advantages that these possess over 
other chemical substances are that they are rapidly diffusible in 
water, and non-poisonous to man and beast. 
(5) The pouring of petroleum on the water has been advocated 
and practised in some places, the oil causing the death of the larvae 
by preventing the latter rising to the surface and thus depriving 
them of their necessary supply of oxygen. This is a method 
which can be adopted in certain localities, though obviously it does 
not admit of anything like an universal application. 
(6) The powder made from the unexpanded flowers of certain 
plants, e.(j., Chrysanthemum and Pyrethrum cinerariaefolium, have 
a germicidal action upon the larvae, and as these plants often thrive 
in malarious districts, it is conceivable that their cultivation on 
the large scale might be the means of rendering such districts 
habitable. 
The odour emitted by certain substances, such as garlic, camphor, 
&c., will cause the death of the Mosquito, as will certain fumes, 
especially tobacco-smoke. The best time of the year to wage war 
against both the Mosquito and its larvse is during the winter and 
early spring months, for at this season they exist in fewest numbers, 
and when more exact information is at hand as regards the habits 
of these insects during the colder months, it is not improbable that 
a considerable destruction of them might be brought about yearly 
by fumigation and other means. 
Eucalyptus trees have been imported and planted in certain parts 
of Italy, with the idea that the oil exhaled from their leaves would 
act as a germicide to the insects, but the experiment did not meet 
with the success that was expected.* 
With regard to the best means of protection against the bites of 
the Mosquito, there are several precautions that should be adopted 
by those living in malarious districts. In the first place, the clothing 
* Indirectly, I believe, the importation of the Eucalyptus into Italy has 
been the means of diminishing the number of Mosquitoes ; for, being trees 
that exhale a large amount of moisture from their leaves, they tend to drain 
the water from the surface soil to their roots, and thus diminish the number 
of breeding places for Mosquitoes. — S. H. L. 
