The system is not often applicable in houses, but aboard ships it is found most effective, the holds of ships being flooded with sulphur dioxide, developed by burning sulphur in a special furnace provided with a pumping and piping system for delivering the gas at distant parts of the ship. In empty ships' holds and elsewhere the simple burning of sulphur in open vessels effects the same results, provided sufficient sulphur and a sufficient number of vessels be used and further provided that the generation and confining of gas be sufficiently prolonged. In San Francisco harbor, where for more than a year nine vessels were disinfected per day, this method was adopted as more effective, speedy and economical than any other system. It has the disadvantage, in the case of laden ships, of affording some danger of fire.
Carbon bisulphide has been extensively used in California in the burrows of ground squirrels. Its fumes, being heavier than air, penetrate the burrows and promptly poison or asphyxiate all living animals and fleas. Absorbent material of some kind is saturated with the liquid and placed in the entrance of the burrow, which is then quickly sealed to confine the gas.
It will be seen that, in common with other methods of rat destruction, fumigation has a limited application and a number of serious objections. It is particularly useful aboard ships.
The method should never be employed by unskilled persons or those unacquainted with the dangers to human life from noxious or asphyxiating gases.
STARVING RATS.--The subjects of the starvation of rats and rat-proof construction may be considered together.
Just as the pig in the Philippine Islands and elsewhere in the Orient must give place as a scavenger of human excreta to modern and decent methods of waste disposal, so must the rat, a garbage scavenger the world over, give place to systematic garbage collection and removal, with temporary storage of garbage in covered metal cans (rat proof).
Incidentally it may be mentioned that the effect of such measures upon the prevalence of flies and the transmission of disease by these insects will be very great and very beneficial to the public health.
Food must be kept from rats and rats must be kept from the food. Perhaps the greatest resorts of rats are the places where cattle are fed, where grain is stored and where animals are killed. Slaughter houses, markets, grocery stores, restaurants, bakeries, wharves and warehouses must be regulated by ordinances duly enforced. Much can be done with screens of heavy iron wire with a mesh of less than one inch.