FUMIGATION. 49 



burrow are asphyxiated. Fumigation in buildings is rarely effective, 

 because it is difficult to confine the gases. Moreover, when effective, 

 the odor from the dead rats is highly objectionable. 



Chlorin, carbon monoxid, sulphur dioxid and hydrocyanic acid 

 are the gases most used for destroying rats and mice in sheds, ware- 

 houses, and stores. Each is effective if the gas can be confined and 

 made to reach the retreats of the animals. Owing to the great dan- 

 ger from fire incident to burning charcoal or sulphur in open pans, a 

 special furnace provided with means for forcing the gas into the com- 

 partments of vessels or buildings is generally employed. 



Hydrocyanic-acid gas is effective in destroying all animal life in 

 buildings. It has been successfully used to free elevators and ware- 

 houses of rats, mice, and insects. However, it is so dangerous to 

 human life that the novice should not attempt fumigation with it, 

 except under careful instructions. Directions for preparing and 

 using the gas may be found in ' ' Hydrocyanic-acid Gas against House- 

 hold Insects," by Dr. L. O. Howard. 



Carbon monoxid is rather dangerous, as its presence in the hold of 

 a vessel or other apartment is not manifest to the senses, and fatal 

 accidents have occurred during its employment to fumigate vessels. 



Chlorin gas has a strong bleaching action upon textile fabrics and 

 for this reason can not be used in many situations. 



Sulphur dioxid also has a bleaching effect upon textiles, but less 

 marked than that of chlorin and ordinarily not noticeable with the 

 small percentage of the gas it is necessary to use. On the whole, this 

 gas has many advantages as a fumigator and disinfectant. It is 

 successfully employed also as a fire extinguisher on board vessels. 



The port regulations for destroying rats to prevent the introduc- 

 tion of plague and to disinfect merchandise and personal effects of 

 passengers have generally been made to conform to the opinion of 

 health officers that thorough fumigation with sulphur dioxid forced 

 into every part of a ship meets all requirements, and the long delays 

 of quarantine are thus avoided. A number of important steamship 

 companies have fitted their vessels with special apparatus for gener- 

 ating the gas and forcing it into the compartments of their ships, 

 and the authorities of some ports have fitted the docks with such 

 apparatus for use on all incoming vessels. 



While the chief object of the port regulations for disinfecting ships 

 is to prevent the introduction of plague and similar diseases, the 

 advantages of having vessels free from rats and other vermin are of 

 sufficient importance to warrant the outlay for apparatus. The 

 numbers of rats on shipboard and the amount of mischief they are 

 capable of are not always appreciated. A French maritime journal 



a Circular 46, Bureau of Entomology, U. S. Dept. of Agric, 1907. 



