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the bottom, and in test-tubes in the burrows,—were killed. Six out of eight rats
on the floor or 4 feet above floor level were killed and seven rats at higher level
were all killed. The rats in burrows A and C were killed. There was some
obstruction in burrow D preventing all the gas entering. Burrow B was the
observation burrow and was opened during the experiment when the rat was
found to be sick. The whole experiment was completed in forty minutes with
an introduction of about 4.38 cubic feet of the gas equivalent to 340 grammes of
98 per cent. potassium cyanide about ¾ oz. to the 100 cubic feet space.

     Experiment IX.—Rats loose in the burrows were also killed.

     Attempts were made to dispense with the complicated apparatus of fans
and tubes by generating the gas inside the room, as described on pages 5 and 6.
They are detailed in Experiments XI and XII. At higher levels of the room
rats and fleas were killed, but rather unsatisfatory results were obtained at floor
levels, and the experiment was an absolute failure in the burrows, both rats and
fleas escaping.

     Therefore, with artificially constructed burrows and the use of an apparatus
with a fan to pump in the gas small rooms can be disinfected thoroughly in, say
one hour.

     Whether natural burrows can be penetrated by the gas remains to be
proved. As the gas is so poisonous, special permission must be obtained before
experiments can be carried out. As far as we can see at present with small
isolated huts when the inhabitants are all cleared out there would be no danger.
The inhabitants could return with perfect safety in two hours after ventilation
was begun, but to make it absolutely sure, say twelve hours.

     When houses are placed close together, as in a Punjab village, the whole
would require to be evacuated simultaneously for two reasons:―

     (1) As rat burrows run from one house to another the gas produced in one
house might find ingress into others causing great danger to the
inmates. The faint almond odour of the gas and the taste at the back
of the throat is only appreciated for the first few moments. The gas
then paralyses the sensory nerves and though dangerous quantities
may be present they would not be appreciated.

     (2) For a successful experiment such contiguous houses should be done
simultaneously in order that no rats may escape.

     With tenements in cities like Bombay evacuation of the whole tenement
would be necessary for the same reasons. Further, a clear space round is a
necessity, as even when only 4 ozs. of potassium cyanide were used in a small
godown the odour of the gas was perceived twenty feet away when the door was
first opened. See also on this point what is noted above on page 6. For these
reasons the wholesale use of the gas is impossible. It ought first to be tried