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1. Rat poisons.—Poison if intelligently used can accomplish much
by means of a 'poison campaign' a rapid redaction in the rat
population can be effected. The chief disadvantage of the method is
the nuisance caused by the decomposing bodies of dead rats, a
nuisance which is small however when compared with the dangers of
plague that rat infestation denotes. The selection of a suitable poison
is the most important consideration. Most of the rat poisons on the
market will kill rats if the rats can be induced to swallow sufficient,
but most of them are distasteful or positively repulsive to rats. All
phosphorus poisons possess this disadvantage ; their inflammable
nature also makes them objectionable. The most satisfactory of all
poisons, and happily the cheapest, is barium carbonate. Barium
carbonate 1 occurs in nature, unfortunately not in any quantity in
India, and is a heavy white tasteless inodourless powder that is almost
insoluble in water. As a rat poison it is certain in its action and
safe to handle. When mixed with flour and water it in no way makes
the mixture less palatable to rats who seem quite unable to detect its
presence in spite of their singularly acute attributes of taste and smell.
Poison baits are best made as follows :—
One pound of powdered native barium carbonate is mixed
thoroughly in an enamelled basin with three pounds of flour made from
the grain which constitutes the staple food of the locality in which
operations are to be carried out. Sufficient water is added to make
the whole into a fairly firm paste. The resulting mass is sufficient for
some 2,400 baits, each containing three grains of poison, which are
conveniently rolled into pill form. Clean hands and dishes are
necessary to avoid imparting to the baits extraneous taste and odour
which may diminish their attractiveness. Baits should be made fresh
each day as a hard stale bait is rarely eaten by the rat,
Poison baits made in the manner described should be laid in the
evening, four baits on a small piece of paper being placed in situations
readily accessible to rats but not so readily accessible to children
and domestic animals. 2 Twelve baits, three groups, will be found
generally sufficient for an average sized Indian room. A careful
record of the baits set should be kept, and in the morning all
unconsumed baits should be collected and destroyed, note being made
of the number consumed wholly or in part, and the dead rats found
should be counted and destroyed. This process can be repeated daily
until no more baits are consumed. Another baiting of the village or
town can be carried out some two weeks later. When baiting is
being carried out special efforts should be made to encourage house-
holders to keep all other available food for rats covered up, especially
at night. In. laying baits the presence of rat holes, or other indica-
tions of the presence of rats, will afford useful indications as to where
baits can be laid with most chance of success.
1 The carbonate is the only salt of barium that should be used. Barium sulphate
or barytes, the most common barium salt, is valueless as a, rat poison.
8 Fifteen grains of barium carbonate will frequently kill a cat ; 20 grains is fatal to
chickens. Dogs can withbtand a dose of 140 grains.